Pathway to Japanese Literature

Monster of the Sunken Ship

The sunken ship salvage work of Nittō Salvage Company was being conducted off the coast of Ōto Village, located on the eastern side of the Bōsō Peninsula.

At the bottom of that sea lies the Tōyō Steamship Company’s 1,500-ton cargo ship *Ashihikimaru*. One stormy night about a month ago, the *Ashihikimaru* had mistaken its course, collided with a massive underwater rock, ripped open the ship’s hull, and sank to the depths.

The salvage company’s work vessel entrusted with raising this sunken ship went to the sea surface above where the *Ashihikimaru* had sunk and, to investigate how best to lift it, first lowered two divers to the seafloor.

Wearing thick rubber suits, donning round iron helmets, and wearing heavy lead-weighted boots, the two divers descended the iron ladder affixed to the exterior of the work ship. With bubbly froth rising around them, they entered the blue sea. The air hose and lifeline extended steadily downward.

It was a place like an underwater mountain range, where large rocks rose up, and the bottom was surprisingly shallow. At just thirty meters below the surface, they were already touching down on the seafloor.

When descending thirty meters, the sea became as dark as twilight, so the divers carried powerful underwater lamps. The electric cable was wrapped around the lifeline and connected to the work ship above. They advanced through swaying kelp forests, swinging their lamps to illuminate the way while pushing through seaweed that grew taller than a man's height—fluttering fronds trembling around them as they pressed forward.

In the distance, a dull black gigantic mass resembling a monster loomed dimly. That was the sunken ship. The two divers pulled their air hoses and lifelines swaying behind them from their iron helmets as they approached the black hull. Right before the round glass windows of their iron helmets, various fish glided smoothly past. Large sharks would sometimes appear out of nowhere and collide with their iron helmets.

The two divers eventually reached the sunken ship and began examining the damaged area. They walked along the black hull lying on its side, moving from the stern toward the bow while illuminating their path with underwater lamps. The sunken ship was like a large iron house at the bottom of the sea. They walked along the long, long iron wall. After walking for a while, the diver who had been standing ahead moved his lamp up and down to signal. They had found the damaged area.

The iron plates on the ship’s bottom had flipped up like a giant’s tongue, leaving a large hole big enough for two people to pass through. If water had come pouring into such a hole like a waterfall, there would have been nothing they could have done. The two divers brought their underwater lamp closer to measure the size of the torn hole. Then something briefly peeked out from inside. They instantly thought there might be a large fish, but it wasn’t a fish. It somehow resembled a human being. Yet this wasn’t an ordinary human—they felt they were seeing a terrifyingly large human face.

However, there could not be any human corpses remaining on this sunken ship. All crew members had been rescued after all. Moreover, what they had glimpsed just now wasn’t a corpse’s face. It was a living person—no, something strange that resembled a human.

The divers had encountered all manner of terrifying things on the seafloor, so they weren’t easily startled—but whatever had just peeked out at them now felt unnervingly sinister. Even these seasoned divers became frightened.

The two divers stood frozen there, exchanging glances for a while, until one fluttered his right hand in front of the underwater lamp’s light. It was a substitute gesture for words. Inside the diving helmets was a telephone device that allowed communication with those on the work ship above, but divers could not converse with each other via telephone. There was also a system where electric wires attached to their hands would enable communication if they clasped them together, but typically such setups were not used.

Japanese divers were skilled at diving to the seafloor since ancient times when advanced diving suits like those of today were not yet available, and had also become accustomed to communicating through hand gestures underwater. Just as a mute person communicates through gestures, divers too could convey anything using only hand signals.

“Are you scared?”

One diver’s hand gestures were saying just that. When asked that way, he couldn’t very well say,“I’m scared.” “Scared? Not a chance! Let’s go inside.”

The other diver answered with hand gestures.

“You go in first.” “No, you’re closer to the hole, aren’t you? You go in first.” The two were arguing over who should enter first precisely because they felt afraid. Yet the bravery of Japanese maritime rescuers was renowned worldwide. They couldn’t possibly admit to fear without tarnishing Japanese divers’ honor. If their comrades learned they’d fled upon seeing something suspicious, they’d become laughingstocks among their peers.

“In that case, let’s hold hands and go in together.” “Yeah, that’s good.” The two divers, holding hands, decided to enter the torn hole in the ship’s hull.

The inside of the hole resembled a large storage room for cargo, but as the underwater lamp’s light was not particularly strong, the far side of the room remained pitch-dark, making it impossible to tell what might be lurking there.

The two stepped over the edge of the hole and slipped lightly into the ship’s interior. And so, they proceeded to walk gradually toward the back of the ship’s hold, its floor steeply tilted. Crates and straw-wrapped bundles lay scattered about. The lightweight cargo had floated up and clung to the room’s ceiling. Also, there were things floating softly before them.

Through that space swam fish of all sizes—large ones and small ones—darting about in every direction. As they drew near the underwater lamp, their scales glittered beautifully with reddish gold and bluish silver hues.

These two had been divers for a long time, so they had seen countless human corpses floating in ship holds like this. Bloated corpses and skeletal remains—they had long grown accustomed to such gruesome sights. Therefore, they knew well that what they had glimpsed earlier was not a human corpse. Of course, it wasn’t a fish either. It was something unknowable. The thought that at any moment that thing from earlier might slither out from behind the cargo ahead made even these seasoned, brave divers feel uneasy, shivers running down their spines.

However, inside that ship’s hold, there was nothing particularly suspicious in sight. On one wall, the door leading from the ship’s hold to the next room stood wide open. The space beyond appeared to be the engine room.

“Let’s try going in here.” “Yeah, alright.”

After discussing with hand gestures, the two stepped through the door to the other side.

A massive steam engine lay in utter silence within the stagnant water. It had the appearance of a machine’s corpse. Since even machines are alive when they’re moving, seeing them lie still as if dead gives off an uncanny feeling. The two had just entered and taken two or three steps when... A truly strange thing occurred. A part of the lifeless machine began to clank into motion.

The two froze in shock. Because there was no way a machine submerged for a month could start moving. Yet when they stared intently, part of the machine was indeed moving.

Before long, a part of the machine separated from the engine and appeared to drift smoothly toward them. It was like a machine ghost. Inside their metal helmets, the two divers screamed, “Agh!” and fled. Paddling the water with both hands, they fled for their lives.

At that moment, the two clearly saw the monster’s form. It had an indescribably terrifying appearance.

It was a living machine. No—it was a living thing that resembled a machine. It had a head, two arms, and a tail like a crocodile’s. All of it seemed to be made of iron, like machinery. The black iron head was about twice the size of a human’s. It matched the dimensions of a diving suit’s iron helmet. On its face glared two large sunken eyes that shone fiercely even in the seabed’s faint gloom. Its mouth split open up to its ears, exposing sharp fangs. The monster beckoned with its thick iron rod-like arms as if saying “Come here,” each iron finger tipped with eagle-like talons. Both torso and tail appeared iron-clad, with jagged protrusions resembling a rooster’s comb or animal’s mane running continuously from spine to tail tip. An indescribably grotesque hybrid of human and crocodile—its entire body forged from iron.

The two divers, without a moment’s hesitation, fled outside through the hold’s torn opening, then via the telephone in their helmets,

“Emergency! Hurry up and pull us up!”

they called out to the salvage ship.

When the two divers were hauled up onto the salvage ship and recounted their encounter with the seafloor monster, chaos erupted. The next day saw even the Maritime Self-Defense Force dispatched to launch an extensive underwater search—yet despite combing through every corner of the sunken ship, the monster never reappeared. In the end, authorities settled on concluding that the divers must have witnessed a phantom of the deep.

The divers, “How could that be a phantom?” “We saw that thing’s form clearly.” “How could both of us see the same phantom?!” insisted vehemently, but nobody would believe them. The two divers then said they’d dive again to investigate, thoroughly searching through the sunken ship—but they never encountered the monster again.

They insisted vehemently, but no one believed them. The two divers then declared they would dive down once more to investigate, thoroughly searching every corner of the sunken ship—but they never encountered the monster again.

Iron Mermaid

Sure enough, around that time, strange things began occurring in Ōto Village—a lonely fishing village on the coast near where the diving operations were taking place.

Ōto Village was a lonely village inhabited solely by fishermen, but among the children of those fishermen was a boy named Sanada Ichirō. His father owned a fishing boat equipped with an engine and was the village’s top fishing expert. Ichiro was a first-year student at the middle school in a nearby town, and his hope for the future was to become an even greater fisherman than his father and engage in deep-sea fishing. For that purpose, a promise had been properly made for him to be enrolled in a specialized school.

Being such a boy, he loved the sea more than anything else. He was a strong swimmer who could easily swim up to four kilometers, and on days off, his greatest joy was boarding his father’s boat to help with fishing. When he couldn’t board the boat or go swimming, returning from school to gaze at the Pacific Ocean from atop a high rocky hill on the village outskirts had become his daily routine.

All alone, he sat atop the rocky hill, resting his cheek on his knees, staring fixedly and endlessly at the sea. The vast sea stretching endlessly all the way to the distant American continent—what a free and beautiful sight it was. Even the same sea could appear astonishingly different in its beauty depending on the time. During the calm of a mirror-like sea when its entire surface foamed and churned; during storms when it seethed like boiling water; when dyed crimson by morning and evening sun; when shimmering silver under full moonlight—each of these scenes held beauty so profound it could melt one's soul.

That evening as well, upon returning from school, Ichiro hurriedly finished his homework, rushed out of the house, climbed up the rocky hill, sat down at its peak, and gazed intently at the sea—vast and motherly like a nostalgic giant.

After a while，the long clouds streaming across the vast sky turned yellow，then gradually reddened until they became a vivid crimson like stained glass．Their hue dyed the wide sea，and water as far as eye could see shimmered beautifully，as though paint had been dissolved into it． When he turned around，a tub-sized crimson sun was now about to disappear behind the mountain at his back．

Just then. Ichiro suddenly looked down at the base of the rocky hill where the waves crashed and spotted some sort of black, strange thing squirming on a rock there—startled, he strained his eyes. Since the coast was a good twenty meters below, he couldn’t make out the details, but there, crouched on the rock, was something strange—something he had never seen before.

“Ah! A black mermaid!”

Ichiro involuntarily let out a cry. The creature had a shape as if a human body were attached to the top of a fish’s tail. Its body was pitch black and jaggedly uneven, but its shape closely resembled that of a mermaid he’d seen in some picture. The mermaids in pictures have a beautiful naked woman with long black hair cascading down her back atop a scaly fish tail, whereas the mermaid now beneath his eyes was pitch-black, angular and blocky as if made of iron, appearing unnervingly sturdy. Moreover, its fish-like tail didn’t have scales gleaming silver but instead resembled a crocodile’s—hard and imposing.

Ichiro had believed mermaids didn't truly exist. Having seen this mermaid that shouldn't exist in this world—moreover an iron-imposing mermaid—now moving across rocks beneath him, he couldn't help doubting his own eyes. He began fearing something had gone wrong with his mind.

However, Ichiro was a courageous boy. Just because he had seen something terrifying didn’t mean he was the type of coward to get startled and flee. Far from fleeing, he instead resolved to get closer and clearly observe that monster’s form.

Following a hidden path, he scrambled down the rocky hill and stealthily peered at the monster from behind a tunnel-like rock formation along the coast. The rock where the monster was perched lay just about ten meters ahead of him.

The sun had completely set, the sky had turned gray, and the sea had darkened to an inky black. White waves crashed violently against the wave-washed edge lined with rocks. On one of those rocks sat a black iron-like creature facing away, utterly still. The monster seen from ten meters away was a chillingly terrifying sight. The crest-like structure on its back stood sharply pointed like an array of swords. Its massive tail resembled an iron crocodile's, looking as though it would clatter and clank with every movement.

Ichiro's breathing grew more intense. Could it be that such a terrifying monster had been living in the Pacific Ocean? They said there were monsters unknown even to zoologists lurking in the deep, deep valleys of the sea—could it be that one of them had suddenly appeared on this Japanese coast?

As he clutched his pounding chest and pondered this, the monster stirred. And then, it suddenly whirled around to face this direction.

Ichiro felt as though his heart had leaped into his throat. Ah, that monster’s face! Ichiro would never be able to forget it for the rest of his life. The sharp crest on its back ran all the way up to the top of its head. Two enormous, sunken eyes—like caverns—glowed blue like phosphorus. The mouth was split all the way to the ears, and from between its lips, sharp fangs jutted out menacingly.

The moment Ichiro saw it, he hid himself in the shadow of a rock, but the monster had already noticed.

“Grind… grind… grind… grind….” An eerie metallic noise—like iron scraping against iron—rang out. It was later learned this sound had been the monster’s laughter. “Hiding won’t work. “I know you’re there. “Come out and hear my words.”

It was the monster’s voice. This seafloor-dwelling monstrosity spoke Japanese. Yet its pronunciation remained maddeningly indistinct—a metallic grinding of iron against iron that demanded intense focus to decipher. Ichiro thought this was the end. He steeled himself for a desperate struggle, certain the creature would seize him and drag him down to the ocean’s depths. Then, gathering his courage, he emerged from behind the rock and met the monster’s gaze.

“You’re strong, aren’t you? What an impressive child.” “If it’s you, you can relay my words to everyone.” “Good. Listen carefully.” “I am the monster of the seafloor.” “I won’t return to this village.” “But mark this—the Japanese will soon face turmoil when I begin my work.” “Tell them all. Declare that the seafloor monster has finally made landfall in Japan.” “Understood?”

Then, no sooner had it let out a grinding metallic laugh—"Grind... grind... grind..."—than a splash sounded, and instantly, the monster’s form vanished from sight. It plunged into the sea where white waves churned.

Iron box.

Now, shifting the story to events in Tokyo.

It was about ten days after the Iron Mermaid had appeared in Ōto Village.

A second-year middle school student named Miyata Kenkichi, who lived in Setagaya Ward, was walking through the shrine forest one night while taking a shortcut on his way home from a friend’s house. Outside was a lonely path that no one traveled at night—a shortcut any ordinary child would find too frightening to take. However, Miyata Kenkichi, being a member of the Boy Detectives Club, actually found walking alone through the dark forest to be rather enjoyable.

The shrine forest was vast, with large trees standing in rows, their branches covering the sky so densely that even daytime was dimly lit—so at night, it became a starless void of utter darkness. Streetlights stood here and there, but their light was blocked by the leaves and didn’t reach far. The stone lanterns lining the roadside looked like giant monk specters, creating an unnervingly eerie atmosphere.

Kenkichi was walking briskly while whistling, but when he reached about halfway through the forest, he thought he heard another set of footsteps besides his own. Hmm? he thought, stopping his whistle and listening carefully as he walked—and indeed, there was another set of footsteps. It wasn't that his own footsteps were echoing through the forest to create a doubled sound. The other footsteps pattered rapidly, sounding as though someone were running.

Kenkichi experimentally came to a stop, but even so, the pattering footsteps continued.

Sure enough, someone was running up from behind.

When he turned around, he saw a dark figure darting out from between the rows of stone lanterns. It was an adult. He might be a villain. He might have been following Kenkichi. And wasn’t he trying to take my money?

However, Kenkichi did not run away and stood still right where he was.

The man immediately approached his side, “Hey, you. I have a request.” “I have an important request.” “Listen,” he said breathlessly.

he said breathlessly.

“To me?” “Yeah, that’s right. I’m being chased by villains right now. Keep this for me. It’s more important than my life. Is your house nearby?”

“Yes, it’s very close by.”

“Then take this back to your house and hide it somewhere no one in your family will find it.” “Inside this box is sealed a terrible secret.” “The villains might kill me trying to steal that secret.” “If I die, throw this box into the river or something.” “But as long as I’m alive, you must never throw it away.” “I’ll definitely come to get it back, so until then, keep it hidden somewhere no one notices.” “Got it?” “It’s something more important than life to me.” “Got it?”

Amidst the darkness, as they spoke like that, the man’s facial features became faintly discernible. He wore a black suit—a wrinkled, dirty suit. He must have been over fifty. His face was deeply lined with a bushy beard. It wasn’t that he was growing it out; rather, days without a razor had left his cheeks black with stubble. That eerie man was carefully holding out a small black box with both hands.

As Kenkichi hesitated, unable to decide whether to accept the small box and remaining silent without replying, the man kept glancing back over his shoulder while—

“Hurry!” “Hurry up and take this.” “I’m being chased by villains.” “They might come here any moment now.” “If they do that，it’s all over.” “The villains are after this small box.” “Come on，hurry!”

The man said this and was looking back again when he seemed to catch some distant sound, startling—

“They’re here.” “They’ve come.” “It’s over.” “I’m begging you.” “Take this and hide it.” “Don’t let the villains get it!” “Here, take it!” “And hide behind that big tree over there.” “Don’t you dare run away.” “They’re adults, so if you run, they’ll catch you right away.” “Got it? You understand?”

The small box had somehow found its way into Kenkichi-kun’s hands. It seemed to be made of iron and, despite its small size, was an extremely heavy box. Because the man shoved Kenkichi-kun in the back, he staggered involuntarily and hid behind the trunk of a large tree. Since it was a place of pitch darkness where no streetlight reached at all, there was absolutely no fear of being discovered by the villains.

When he confirmed that Kenkichi-kun had hidden himself, the man suddenly broke into a run—but seemed too exhausted to move swiftly. From behind came the sound of vigorous footsteps closing in. Tap-tap-tap-tap—a terrifyingly rapid staccato of steps.

Before Kenkichi-kun’s eyes—peering cautiously from behind the tree trunk—a young man’s figure appeared, slicing through the wind. He looked like some thug wearing a gaudy striped suit.

In no time, he caught up to the fleeing man.

“Stop! You’re not getting away now!” “I know damn well you ran off with the iron box.” “Hand that over here.”

In response to the young thug’s brazen shout, the Fifty-Year-Old Man answered feebly.

“I don’t know anything about an iron box.” “Go ahead and look.” “I don’t have that thing anywhere.”

The young man seemed to be searching all over the Fifty-Year-Old Man’s body. However, since the iron box had long since passed into Kenkichi-kun’s hands, there was no way it could turn up anywhere.

“Damn it.” “You hid it somewhere, didn’t you?” “Come on, confess!” “Where did you hide it?” “If you don’t talk, I’ll make you suffer.” The young man gripped the Fifty-Year-Old Man’s hand and twisted it behind his back. However, the man did not utter a single word. Not only that—now fighting for his life—he wrenched his hand free and suddenly lunged at the young thug.

A terrifying struggle began. The two of them grappled fiercely in the darkness, tumbling down and rolling over each other across the ground, but there was no way the Fifty-Year-Old Man could match the young thug. Before he knew it, he had been subdued by the thug and was letting out an ominous groan.

The young man had straddled the Fifty-Year-Old Man and was choking his neck with both hands. The man beneath him might die. He had gone completely limp and seemed unable to utter a sound.

Kenkichi-kun thought about dashing out from behind the tree to help him, but if he did that—since he stood no chance against the thugs—the iron box might be taken. If it were taken, he wouldn’t be able to face the man. Since this was the box he wanted to hide even if it cost him his life, no matter what happened, he couldn’t hand it over to the villains.

While he busily considered these things and hesitated, the young thug appeared to release his grip and rise.

“I’ll spare your life. “Gotta keep you alive till I get that iron box—or the boss’ll have my head. “Heading back now to consult him properly. “That box’ll be mine no matter what—you better remember that.”

The young thug said such things and disappeared off somewhere. Though he pretended to leave, Kenkichi-kun watched for a while, suspecting he might be hiding somewhere. But even after some time passed, nothing happened—it seemed he had truly left—so Kenkichi-kun timidly emerged from behind the tree and approached the collapsed man. The man appeared completely lifeless, but when Kenkichi-kun peered at his face and tried to lift him up, he finally opened his eyes and let out a pained groan.

“Ah, you…” “They got me.” “I’m done for.” “I’m counting on you with the box.” “When I die, throw it into the river.” “Even if this ends up involving the police, keep quiet about the box.” “I don’t want the police to find out either.” “You mustn’t tell even the people at your house.” “I haven’t done anything wrong.” “You won’t get dragged into any trouble because of this, I swear.” “Listen, I’m counting on you.”

That was all he could manage to say. The man closed his eyes again just like that and went completely limp.

Kenkichi-kun, realizing he couldn’t handle it alone, suddenly dashed off, emerged from the shrine’s forest, returned to his nearby home, and reported everything that had happened to his father. He hid the iron box in a drawer of his study bookshelf and didn’t even tell his father about it. After calling the police, his father decided to go into the forest with Kenkichi-kun as his guide.

The Face in the Window

The Fifty-Year-Old Man who had entrusted the iron box to Kenkichi-kun passed away four or five days later at the police hospital. Upon investigation, it was discovered that this man was a homeless former sailor with neither family nor relatives—a complete loner—so the police admitted him to a hospital for treatment, but as he had always been physically weak, he ultimately passed away.

Now that the man had died, Kenkichi-kun was supposed to discard the iron box into the river as promised, but he simply couldn’t bring himself to throw away something that supposedly held such a great secret. He wanted to quietly keep it hidden and investigate its secret himself. Therefore, even though it meant breaking his promise, he decided to keep it hidden for a while without discarding it.

The box was a black iron case measuring approximately fifteen centimeters in length, nine in width, and six in thickness, carved with a pattern of dried grass. It had no visible seams, and there was no discernible way to open it. What was inside it? Even when shaken, it made no sound at all.

Kenkichi-kun felt as though some extraordinary treasure might lie within, making him reluctant to hastily destroy the box. He resolved to examine it thoroughly later and needed to conceal it somewhere no one would discover. After weighing various possibilities, he settled on hiding it beneath an appropriately sized rock in the garden's earthen mound. On the night of the forest struggle, once everyone had fallen asleep, he quietly slipped out through his bedroom window, dug under the rock with a toy shovel, and buried the iron box there.

On the evening when he received news that the man had died at the hospital, he lifted the stone to check, but the iron box was still there properly.

However, there was one thing that worried Kenkichi-kun. After the struggle in the forest, when he returned home, the knife he had placed in his coat pocket was missing. It was a small pencil-sharpening knife, but while hiding in the shadow of a tree and watching the struggle unfold, he had unconsciously gripped that knife in his hand. He hadn't meant to hurt the thugs with it—his hand had simply moved on its own and clenched the blade. He thought he'd put it back in his pocket afterward, but in his panic, he might have accidentally dropped it.

The knife had a deer antler attached to its outer side, but unfortunately, his name—K. MIYATA—was carved in Roman letters on the surface of that antler. If that knife were picked up by the thugs, they might realize Kenkichi-kun had hidden the iron box. So the next day, during daylight hours, he went into the forest and searched every corner of the area, but the knife was nowhere to be found. Could those thugs have come back later and taken it? For Kenkichi-kun, this remained his sole concern.

Now, it was one evening about fifteen days after the man had died in the hospital.

Kenkichi-kun was at his study room desk working on his school homework. It was already around nine o'clock at night. That day too, after verifying that no one was watching in the evening, he had peeked under the rock on the earthen mound and confirmed that the iron box remained securely in its original place. And then, feeling reassured, he had been studying. From the looks of it, whoever picked up the knife didn't seem to be one of the thugs. Even though half a month had passed since then with nothing happening around Kenkichi-kun, he had come to feel that it was safe now.

However, that was not the case.

Because he had reached a difficult part in his homework, Kenkichi-kun set down his pencil and stared into the space before him to think. Then, right before his eyes, there was something hazy shifting about. "Oh?" he thought, steadying his gaze to look there.

On the other side of the desk was a glass window. Because the curtains weren’t drawn, the pitch-black garden was visible through it. In that pitch-black darkness, something black shifted hazily. Since it was a dark shape within the gloom, he couldn’t distinguish it clearly, but there was undeniably something present. He thought it might be human, but any human face would have shown pale. It didn’t seem human at all. Not human—yet something human-sized.

A chill ran down his back. The black thing was gradually drawing closer. It came right up to the windowpane. A vague shape came into view. It was a grotesque, eerie thing unlike anything he had ever seen before.

He jolted in shock, his heart leaping into his throat.

Because the thing had pressed its face tightly against the windowpane and was glaring at Kenkichi-kun.

The area below its forehead was sunken like a gorilla’s, and from within that hollow peered two eyes glowing with a bluish-white light like phosphorus. Its mouth was split open all the way to its ears, and from between those lips, two fangs slid out smoothly. It was not a human face. Nor was it an animal’s face. It was some sort of unidentifiable thing. The entire face was shining with a black luster, just like iron.

Kenkichi-kun tried to flee. But when those phosphorus-like glowing eyes glared at him—just like a frog paralyzed under a snake’s stare—he found himself utterly immobilized, left with no choice but to remain frozen in his chair.

Then, something even more terrifying happened. The glass window began creaking open upward from below. The monster was opening the sash window from outside. Even so, Kenkichi-kun still lacked the strength to flee. It was as if he'd been bound to the chair—his body refused to move at all. His eyes remained locked on the monster; though he tried to look away, he couldn't wrench his gaze free.

The window was opening little by little, upward. And when it had opened about forty centimeters, the monster’s face slid into the window. The two eyes were burning like blue flames. On top of its head, a sinister crest-like structure stood sharply upright. And then its mouth… Its mouth—split open all the way to its ears—opened with a creak into a crescent shape, “Grind... grind... grind...”

It laughed. With a terrifying sound like iron grinding against iron, it laughed.

The Monster’s Whereabouts

Kenkichi-kun instinctively cried out “Waaah!”, stood up from his chair, and tried to flee toward the door—but at that moment, his head spun, his vision went dark, and he lost consciousness, collapsing right there.

“Hmm, that sounded like a strange noise just now.”

Kenkichi-kun’s father came out from the back room into the living room.

“It seems to be coming from Kenkichi’s room. What could be wrong? Would you mind going to check?”

Mother had also risen to her feet with a worried expression. "I’ll go check." "Toda, come along with me."

Father hurried to Kenkichi’s study room, taking along Toda, the live-in student who had been in the hallway. “Ken, did you make any noise just now?”

Even when they called out from outside the door, there was no response. And inside the room, a strange clattering sound was coming from somewhere. “Who’s there?” Toda, the live-in student, shouted and tried to open the door but discovered it was locked from the inside. “That’s strange. “Ken-chan hardly ever locks the door.” “…There was another identical key in the living room.” “I’ll go get it.”

Toda ran off with those words but immediately turned back and opened the door with the key.

And when they took one look inside the room, the two of them couldn’t help but let out a startled “Ah!” But Kenkichi wasn’t merely lying there unconscious. The bookcase and desk drawers had all been pulled out, their contents strewn about the entire room.

Father rushed over to Kenkichi-kun’s side, lifted him up, and shook him gently while calling, “Ken-chan! Ken-chan!” Then, Kenkichi-kun finally came to his senses, opened his eyes, and suddenly clung to his father. “What’s wrong? What on earth happened here?” Father looked around the scattered room and the opened window, then asked suspiciously.

Still clinging to his father, Kenkichi-kun gently looked around the room but realized that the terrifying creature from earlier was nowhere to be found. “From the window... a monster... came in!” “A terrifying creature with scales covering its body and fangs.” “I thought I was going to be eaten by it.” “It must have gone out through the window.” “It might still be in the garden.”

Kenkichi-kun was trembling uncontrollably as he said this. Father did not believe such a monster existed in this world, so he suspected Kenkichi-kun had seen a dream or an illusion—yet it was strange how the room lay in disarray as if it had been clawed apart. Father rushed to the open glass window and scanned the pitch-dark garden. However, there was no sign of anything in the garden.

“Ah!”

Father noticed terrifying claw marks had been left on the windowsill at that moment. They were vivid gouges resembling five large, sharp claws digging deep into the wood. "Hey Toda, look at these marks." "Don't these look like some sort of animal's claw marks?"

“That’s right. There were no such marks until this morning. Perhaps... it’s possible that a suspicious someone really did break in.” Toda, the live-in student, had also turned pale.

“Alright, let’s go check the garden. There should be footprints. You, bring the flashlight.”

Kenkichi-kun had been clinging to his mother, who had come to check on the commotion, and was trembling. Father and Toda left the room and headed toward the garden. When the two descended into the garden and investigated with a flashlight, they discovered that in the soft soil, there were truly horrifying monster footprints left behind. It was something that could only be considered the footprints of a giant animal with sharp claws.

Seeing such evidence, they could no longer leave it be. Father immediately called the police and informed them of what had happened. Upon receiving the call, the police found it strange, but since Kenkichi-kun’s father was a prominent businessman in town—serving as an executive at a major company—they reasoned it couldn’t possibly be a hoax. Three officers promptly sped over to Kenkichi-kun’s house by car. And then, they searched thoroughly inside the house and garden, but aside from the claw marks on the window and the footprints in the garden, they could discover nothing else.

So having decided to investigate the perimeter of the house, while the three police officers were walking through the dark town outside the wall, they saw a man running toward them from ahead with terrifying urgency—as though being pursued by something, he was charging headlong. “You there! What’s happened?”

When they called out suspiciously, the man stopped in front of the three.

“Oh! You’re officers right?” “It’s terrible!” “A terrifying creature came out from inside the manhole!” He was gasping for breath and looked ready to bolt again. He appeared to be a shop employee from somewhere nearby—a young man wearing a jumper.

“What on earth did you see?” “It’s a monster.”

Hearing this, the police officers thought that this man might have encountered the monster that had attacked Kenkichi-kun and hurriedly questioned him. “Where’s this manhole you’re talking about?”

“Over there. It’s around the corner of this town.”

Upon hearing this, the police officers shouted "Alright!" and suddenly dashed toward that town corner.

As they turned the corner, the manhole came into view immediately. However, there was nothing particularly suspicious in sight. The manhole had its iron lid securely shut.

“Hey, this manhole? There’s nothing here at all.”

When they asked the timidly following young man, he pointed fearfully and—

“It’s that one.” “The lid slowly lifted up... and a terrifying monster came out from inside!” “What kind of terrifying monster was it?” “It had fangs.” “And scales.” “Its eyes glowed phosphorescently.” It really was identical. This was the very monster that had attacked Kenkichi-kun.

“It might not have come out of the manhole—it might’ve escaped into it instead.”

One of the police officers, visibly unnerved, stared at the manhole cover before them.

“Alright, then let’s check it out. Lend a hand—and you, draw your pistol and stand ready. If you sense danger, open fire.”

The officer who appeared to be the senior among the three said this, turned on his flashlight, and crouched down next to the manhole cover. Another police officer assisted him. The remaining officer drew his pistol from his hip holster and assumed a firing stance.

“There we go. Ready?” The two police officers worked together to wrench open the iron manhole cover and move it aside. The inside of the hole was pitch black. The flashlight’s beam swept over there, illuminating it.

Was the iron-scaled monster crouching inside there? No, that was not the case. The inside was completely empty. The police officers were deflated.

“Oh... There’s nothing here at all.”

It was a sewer manhole, but given how narrow the drainage pipe was, escaping through there via the sewer would have been impossible.

The monster must have hidden inside the manhole temporarily and then escaped again. What the shop employee had seen earlier must have been the moment it was emerging after all. This shop employee had seen the same monster as Kenkichi-kun. Since two people had now seen it, it could no longer be dismissed as a dream or illusion. It could not be ignored. Thereupon, the police officers reported this matter via telephone to their local police station, and the local station then contacted the Metropolitan Police Department.

After that, it was a tremendous uproar. No fewer than three patrol cars arrived. Numerous vehicles came from the Metropolitan Police Department and police stations. And newspaper reporters too. Kenkichi-kun’s house became the temporary investigation headquarters, with over ten automobiles lined up in front of the gate, and neighbors gathering to see what was happening—so it instantly became a teeming crowd of people.

A large-scale search involving dozens of police officers began. Every nearby house was searched one after another, police cars patrolled every town, barricades were set up, and a dragnet was cast so swiftly that not even an ant could slip through.

However, even when the next morning came, nothing suspicious was discovered anywhere. The Iron Mermaid had vanished like smoke.

The next day’s newspapers were filled with articles about the Iron-Scaled Monster. The claw marks left on Kenkichi-kun’s windowsill and the large animal footprints in the garden had been photographed and published in the newspapers. People all over Japan read the newspapers and trembled in fear. And whenever people gathered, their conversations were dominated by talk of this terrifying monster.

The Massive Gold Ingots

The next morning, after waiting for the police officers to withdraw, Kenkichi slipped out into the garden. He needed to inspect the small iron box he’d hidden beneath a garden stone. He couldn’t bear the worry that the monster from the previous night might have stolen it.

When he lifted the marker stone—ah, thank goodness. The iron box was there. It had remained properly in its original place. Kenkichi-kun thought he could no longer keep it hidden by himself. He took out the box, hurried into the house, showed it to his father, and explained in detail: how during that nighttime struggle in the shrine forest, a dirty-looking man with a beard all over his face had entrusted him with this box; how the man had told him to throw the iron box into the river if he died; but even after the man passed away at the police hospital, Kenkichi couldn’t bring himself to discard it, so he buried it beneath the garden stone instead.

Father picked up the iron box and tried to open it, but he simply couldn’t get it to budge. The live-in student Toda-kun also tried opening it, but still had no luck.

At that moment, Kenkichi-kun spoke up in a cheerful voice, as if he had just thought of something.

“I have a good idea. I’ll take this box to the Akechi Detective Agency and show it to our Boy Detectives Club leader, Kobayashi. Then, if we borrow Detective Akechi’s wisdom, we’ll definitely figure out this box’s secret!”

“Yeah, that’s a good idea. Have Toda accompany you and take the usual hired car we always call. With both the driver and Toda there to guard you, it should be safe enough. And it’s broad daylight, after all.”

Since Father had approved, they first called Akechi’s office and learned that both Detective Akechi and Kobayashi were present there. Then, after calling for the familiar driver’s car, Kenkichi carefully cradled the iron box and got into it alongside Toda, the live-in student.

When they arrived at the office, Kobayashi came out and guided the two to the reception room. Then, after listening to Kenkichi-kun’s account and taking the iron box in hand to try various methods, even Kobayashi couldn’t open it.

“Wait here a moment. I’ll go show this box to Detective Akechi.”

With those words, Kobayashi took the box and left through the door—but after about ten minutes, he returned smiling alongside Detective Akechi. “Detective Akechi opened it without any trouble. “Look, you do it like this. “It’s just like a Hakone puzzle box. “Press this part here with the karakusa pattern. “Then, this side will open up. “Then press here, see? “Just repeat the same thing two or three times. “Then, it’ll open right up.”

"But more than that, there's something far more serious. Inside this box was something of extraordinary value worth tens of billions of yen."

As he was still reeling from Kobayashi’s explanation, Detective Akechi sat down in a chair and began to speak with a smile.

“It goes like this,” Detective Akechi began. “Inside this iron box were three sealed documents. One is the will of a man named Fukunaga, formerly captain of the ocean-going vessel Taiyōmaru. Another is a nautical chart of waters south of the Kii Peninsula. The third is an insurance company certificate.”

With that, Akechi showed several handwritten notes he had been holding. “Now, the former captain’s will is written in rather complex language, so to put it simply—about twenty years ago, a steamship called the Taiyōmaru sank off Shionomisaki on the Kii Peninsula due to a violent storm.” “It was a once-in-decades storm so severe that even when the Taiyōmaru sent wireless distress calls, rescue ships couldn’t be dispatched from the coast. Many passengers and crew members perished.”

Clinging to a drifting boat, they finally managed to reach the coast—only a dozen crew members remained, among whom was a man called Captain Fukunaga. "A captain who saves only himself isn’t very admirable, is he?" When the Taiyōmaru radioed for help, it naturally reported its current position—but Captain Fukunaga’s will states that in his panic at that moment, he made a grave error. He had mistakenly relayed the longitude figure to the radio operator, making it appear as though the Taiyōmaru had sunk in a completely different location. Later, after the insurance company paid the claim to the shipping company, they investigated the sinking site only to find it was at an extreme depth where neither the ship nor its cargo could be salvaged, forcing them to abandon the effort.

“Captain Fukunaga apparently realized about a year later that the sinking position he had radioed was incorrect—but there was something rather strange about this,” “The captain might have deliberately chosen not to notice,” “And then, after about another year had passed, he purchased the rights to the sunken Taiyōmaru from the insurance company,” “Back then, it was around 200,000 yen—which would be about 100 million yen today,” “He raised that money and claimed ownership of the sunken ship,” “After all, since it was deemed unsalvageable, the insurance company sold it off cheaply.”

The reason he invested such a large sum in a ship with no salvage prospects was that the vessel carried a great many gold ingots being sent from Hong Kong to America. "The will states its value at that time was four million yen, which would amount to about two billion yen today." "The captain tried to salvage them and become wealthy, you see." “Since he had purchased the rights from the insurance company, there was no need to hold back from anyone.”

The insurance company sold the rights because they believed it lay at a depth beyond any salvage technology in the world, but Captain Fukunaga knew full well that the Taiyōmaru had sunk in shallower waters—five miles away from the location reported via wireless. "He figured salvage operations would be feasible there." So when he finally began making preparations to commission a salvage company and recover the gold ingots, Captain Fukunaga was struck by a grave illness, became incapacitated, and died three months later. "It must have been divine punishment, I suppose." So while he could still write, he composed this will, had an iron secret box crafted, sealed it with the insurance certificate and nautical chart marking the Taiyōmaru's true resting place, and left it to his only son.

“That’s why the son entrusted the iron box to Kenkichi-kun,” Akechi explained. “This son was a spineless man who couldn’t even begin salvage operations himself. Though he tried hawking the salvage rights to several wealthy men, he’d become so destitute and disheveled by then that no one would believe such a fantastical story as ‘The Great Gold Ingots of the Seafloor’ from someone like him. Before anyone knew it, twenty years had passed. The son himself wrote about all this at the beginning of the will, you see.”

Detective Akechi’s lengthy explanation finally came to an end.

There were still parts that Kenkichi didn’t fully understand, but regardless, the fact that two billion yen worth of gold ingots lay sunken off Shionomisaki somehow began to feel real to him.

Monster in Broad Daylight

After giving that explanation, Detective Akechi said the following to Kenkichi-kun and Toda, the live-in student.

“The ones targeting this small box are terrifying villains. Sending it back to Kenkichi-kun’s home would be worryingly risky. However, I will protect it for you. It’s perfectly safe now—return home without concerns. And make sure to hide it again beneath the original stone, understood?” With that declaration, he walked to the office desk in the corner of the room, inserted documents into the small box, sealed it exactly as before, and handed it to Kenkichi-kun.

Kenkichi-kun and Toda, the live-in student, expressed their heartfelt thanks to Detective Akechi and Kobayashi, took their leave, and boarded the car waiting outside.

The car started heading toward Kenkichi-kun’s home in Setagaya, and after about fifteen minutes, it came to a desolate road lined with large estates. On both sides stretched 100-meter-long high concrete walls, within which stood large trees that made the area dim even during the daytime.

When they came to a valley-like space between the concrete walls, the car screeched to a halt with a loud brake noise.

“Huh? You’re stopping in such a strange place.” “What’s going on?” “Did something malfunction?”

The live-in student Toda called out to the driver. Then, the driver who had been facing away suddenly turned toward them and grinned. “Ah! You’re not the same driver as before.” “When did you switch places?” “And just who on earth are you?!” “That’s how it goes.”

The driver answered in a brazen voice and thrust the pistol forward with a swift motion.

“Ah! Then you’re…!” Toda exclaimed in shock as he pulled Kenkichi-kun close in a protective embrace. With their opponent brandishing a pistol, there was no way to resist. “Relax,” sneered the driver, “I’m not here to take your lives.” The pistol gleamed dully in his hand as he leaned forward. “Just hand over the iron box.” His voice sharpened like drawn steel. “Now.” Toda’s fingers crept toward the door handle, every muscle tensed to leap from the car at the first opening.

Then, the driver had already anticipated this and sneered with malice. “Ha ha ha… No good, no good. Even if you try to run, you won’t escape.” “Take a good look outside the door.” Startled, he looked out the glass window—there stood a man with a fearsome face right beside the window, having appeared out of nowhere. In his hand gleamed a pistol as he smirked slyly. Then, glancing toward the opposite window from this side—what now? There glared another ruffian of the same ilk, pistol aimed menacingly.

With pistols aimed at them from three sides, there was nothing more they could do. Toda gestured to Kenkichi-kun with hand motions to hand over the iron box. Kenkichi-kun, having no other choice, handed it over to the previous driver.

The man snatched it away and sneered maliciously once more. “Wahahaha… Impressive, impressive! You lot sure know how to follow orders.” “Alright, I’ll let you off this time.” “Your driver’s been stuffed into the back trunk.” “Once we’re out of sight, go ahead and open the trunk to let him out.” “Then he’ll drive you around again.”

The fake driver jumped out of the car and slammed the door shut. Then, the three men began running toward the other side with terrifying speed, like sprinters.

“Ah, I did something irreparable.” “They took that important iron box.” “Ken-chan, those guys are underlings of the villains from before... Still, Mr. Akechi had assured us it would be safe since I was protecting it—what does this mean?” “If it could be taken this quickly, even Mr. Akechi isn’t reliable.” “It’s truly regrettable.”

Toda grumbled resentfully under his breath, but once the three men had disappeared from view, he got out of the car after a while and opened the rear trunk lid. Inside was that familiar driver, gagged, curled up, and crammed into the space.

Kenkichi-kun also got out of the car and helped. And after taking him out of the trunk and removing his gag, the driver rubbed his head while, "When I carelessly parked outside Mr. Akechi's office and let my guard down..." "He suddenly struck me from behind right here and forced this gag into my mouth." "The man was terrifyingly strong—I couldn't resist at all." "I'm deeply sorry." "So that scoundrel disguised himself as me and drove you all here?"

“That’s right,” said Toda to the driver and Kenkichi-kun beside him, his voice tight with frustration. “He wore a jacket just like yours—we couldn’t tell you apart from behind.” He shook his head, the daylight audacity of the ambush still shocking him. “Who’d imagine they’d pull such a bold stunt in broad daylight? Now drive—quick! We’re nearly home.” He gripped the seat as the car lurched forward, adding grimly, “We’ll call the police once we arrive. They’ve stolen something vital from us.”

Thereupon, the three got into the car, but just as the vehicle was about to start moving, Kenkichi-kun let out a cry: “Ah!” His face turned deathly pale, his eyes grew so wide they looked ready to pop out. He was staring fixedly out the window.

Toda and the driver, startled, looked at where Kenkichi-kun was staring.

Something peered over the high concrete wall. Behind it spread large tree branches in a bluish-black tangle. Atop the wall before them loomed something black. It defied description—a grotesque apparition. Two phosphorus-blue eyes glowed within its obsidian face. A gaping maw stretched ear to ear. Razor-sharp fangs jutted from that chasm. From its crown rose a jagged iron crest.

It was the Iron Mermaid. That monster was scaling the inner side of the concrete wall, sticking out only its head, and glaring straight at us.

“Hurry, hurry…” Having encountered it once before, Kenkichi-kun knew full well how terrifying it was. As if the monster might vault over the wall and come chasing after them at any moment, he pressed the driver to hurry.

The driver, thoroughly terrified by this dreadful monster, suddenly stepped on the accelerator. The car plunged forward like a madman through the deserted valley town.

Hayabusa Maru

When Kenkichi and the others returned home, they jumped out of the car and rushed into his father’s room. And, panting, they conveyed what had just happened. His father immediately called the police to report the incident, then summoned the Akechi Detective Agency.

“What? The iron box was taken?” “Just as I expected.”

Detective Akechi on the other end of the line paused thoughtfully after saying this, but quickly continued speaking.

“Well then, I’ll come to your place right away.” “There are matters I can’t discuss over the phone.” “However, please rest assured.” “I promised Kenkichi-kun that I would definitely protect him.” “I have kept that promise properly.”

And then the call ended, but what on earth was Detective Akechi talking about? Hadn't he promised to protect the iron box? That box had already been stolen. What was he trying to do now, at this late hour? Father tilted his head quizzically.

After a short while, Detective Akechi arrived by car. Father and Kenkichi-kun ushered Akechi into the parlor and received him.

“I didn’t quite understand your earlier phone call, but it sounded like you said you’d protect the iron box at all costs.”

Father asked Akechi accusingly.

“That’s correct. I have indeed kept my promise.”

The famous detective answered with a smile.

“Huh? How on earth does that make sense?” “The iron box was taken by the villains.” “No need to worry. Only the box was taken. The contents are safely right here.”

Akechi took out a large envelope from his pocket and, from inside it, produced and showed the captain’s will, the nautical chart, and the insurance company’s certificate.

“Ah! Then that means you… Detective…!” “Exactly. Anticipating something like this might happen, I had switched the contents of the box beforehand.” “The iron box those villains stole contains nothing but blank paper.”

Both Kenkichi-kun and his father were thoroughly impressed by the famous detective’s flawless methods.

“Ah, I had no idea you’d done that, so I’ve been terribly rude.” “Please forgive me.” “As expected of Detective Akechi.” “This has put my mind completely at ease.”

Father kept repeating his words of gratitude. Akechi, rephrasing his words,

“Mr. Miyata, there’s no telling what further schemes those villains might devise from here on out.” “How about we quickly retrieve the gold ingots on our end?” “What’s written in the will isn’t a lie.” “After Kenkichi-kun returned earlier, I looked into it and confirmed that it’s certain the Taiyōmaru of Toyo Steamship Company sank off Shionomisaki twenty years ago.” “Moreover, it’s certain that at that time, attempts were made to conduct salvage operations but were unsuccessful.”

“It’s worth giving it a try. Consult with Toyo Steamship Company and the insurance company to have them provide the funds. If the gold ingots are found, agree to divide them between you, the steamship company, and the insurance company. Notify the government as well, and then explore the seabed—how does that sound?”

Kenkichi-kun’s father had been thinking for a while, but finally spoke with resolve.

“Well then, shall we undertake an undersea adventure? Fortunately, I have friends who are executives at this steamship company and the insurance company, as well as a close acquaintance at a salvage company that recovers sunken ships. If I consult them, they will surely agree.”

“Actually, I’m quite fond of this sort of adventure.”

Then, just as they were discussing various aspects of the gold ingot salvage operation, a phone call came in. Father stood up and went to answer it, but when he put the receiver to his ear, he heard a peculiar noise. It was an eerie noise, like iron scraping against iron—clang, clang, clang, clang. He thought it might be a phone malfunction, but that wasn’t the case. Something was speaking.

“Akechi’s there. There’s something I want to discuss—call him.”

It was an eerie sound that could not be considered a human voice. “Who are you?”

“Akechi’s comrade. Call him quickly.”

Having no other choice, he called Akechi and handed over the receiver.

“I am Akechi, but who are you?”

“You know who I am—your enemy. You hid what was inside that iron box you were protecting. Remember this—I’ll take it back without fail. Akechi—mark my words.” With a metallic clang, the call disconnected. Akechi and Kenkichi’s father locked eyes across the room. “The Iron Mermaid,” Akechi stated. “Just as I thought—that thing is targeting the gold ingots. We mustn’t grow complacent. We need to start the salvage operation immediately.”

The next two weeks passed without incident.

And then, one day, the Hayabusa Maru of Nittō Salvage Company departed from Osaka Port toward Shionomisaki.

The Hayabusa Maru was a six-hundred-ton salvage vessel. Onboard this ship were not only engineers, divers, and crew members from the salvage company but also Kenkichi-kun; his father, Mr. Miyata; and Kobayashi, the boy. They had come from Tokyo to Osaka by train and boarded this ship. Kobayashi accompanied them as Detective Akechi’s proxy. And it had been agreed that if any difficulties arose, they would notify Detective Akechi by wireless.

It was spring. The sky had cleared to a vivid blue, and the Hayabusa Maru glided smoothly across a sea as calm as tatami matting. The voyage was pleasant. Kobayashi and Kenkichi went up to the upper deck, watched the white waves foaming at the stern, linked arms, and sang out resoundingly.

That night was a beautiful moonlit night. As the night deepened, the moon grew increasingly brighter, casting its reflection upon the waves until the sea seemed to scatter silver flakes across its expanse. Except for the crew members standing watch, everyone had entered their cabins and gone to sleep. The thrum-thrum-thrum-thrum of the engine, the swish... swish... of the ship cutting through waves—beneath the moon’s brilliant glow, there were no other sounds to be heard.

A sailor walked clomp-clomp across the deck. It was his hourly patrol. He passed through the narrow passage beside the central cabin and emerged toward the bow. Passing under the hoisted lifeboat and glancing ahead, he saw a black thing crouching at the very tip of the bow.

“Oh? Is someone sleeping over there?” Thinking it strange, he approached, but it didn’t seem human at all. Its entire body was covered in large scales. They sparkled under the moonlight. It had a long tail. From its head down to its back ran a jagged comb-like structure. It somehow resembled a large crocodile. But there shouldn’t be crocodiles living around here.

The sailor felt a chill run down his back. It was a strangely eerie thing unlike anything described in any animal book. But driven by morbid curiosity, he continued sneaking closer, muffling his footsteps—and then the black creature jerked its head up and turned sharply toward him. When he caught sight of it, the sailor’s body went numb, rendering him unable to flee or scream.

On its large face—black like iron—sunken eyes shone like phosphorus. From its crescent-shaped mouth—split open to the ears—white fangs slid out smoothly. “Grind… Grind… Grind… Grind… Grind…….” The monster opened its mouth wide and was laughing. That laughter was an eerie sound, like iron scraping against iron.

“Waaah!”

Finally, his voice came out. The sailor mustered a desperate voice and called out for help.

“Someone… come here…”

At that cry came the sound of running feet from somewhere, and one by one—first one, then two, then three sailors came rushing over. The monster at the bow let out an especially raucous laugh, swiftly twisted around with its scales glinting, slipped past the ship's railing, and plunged into the sea with a splash. Rushing to the ship's side and peering over, they saw an iron-crocodile-like creature swimming alongside the vessel—but in the blink of an eye, it sank deep into the water and vanished from the surface.

It was the Iron Mermaid. Because it had failed to steal the nautical chart from the iron box, it must have secretly pursued Kenkichi and his group all the way to this ship. Though it had plunged into the sea, that thing was a sea monster by nature. It might have been swimming at the same speed as the vessel. And it might have been following Kenkichi and his companions with relentless persistence wherever they went.

The skeleton in the cabin.

Kobayashi, the boy leader, notified the Tokyo Metropolitan Police Department of this incident via wireless and had them relay the information to the Akechi Detective Agency.

After that, with no further incidents, the Hayabusa Maru arrived off the coast of Shionomisaki. The nautical chart obtained by Mr. Miyata clearly marked the latitude and longitude of where the Taiyōmaru had sunk, so they simply needed to explore the seabed at that location with an underwater detector.

An underwater detector was a machine that emitted ultrashort waves from the ship, which hit the seabed, and whose return time was converted into a graph that appeared on paper. The curve of this graph showed the sea depth, but if a sunken ship existed, only that area would appear as a sudden bulge in the line on the graph, allowing them to identify it. The Hayabusa Maru went back and forth across the sea surface marked on the nautical chart, repeatedly examining the underwater detector's graph. And they confirmed that the bulge in that curve was not from seabed rocks or similar formations—it had to be a sunken ship.

From the sea surface to the upper part of the sunken ship was a mere thirty meters. In that case, they might be able to salvage not only the gold ingots but the Taiyōmaru itself. Because the captain of the Taiyōmaru had concealed the true sinking location, the valuable gold ingots and iron materials had lain dormant on the seabed for twenty years.

Once the sunken ship’s location was determined, it was finally decided to send down the divers. Since the captain’s will contained no information about where the gold ingots had been stored aboard the Taiyōmaru, even just locating them would be no easy task. Therefore, they wouldn’t be immediately salvaging the gold ingots—this dive was first and foremost to confirm whether the sunken ship was indeed the Taiyōmaru.

That day, the sky stretched clear and azure—a perfect weather for diving with no wind or waves. The salvage company personnel selected two skilled divers, dressed them in rubber diving suits, fitted them with brass helmets, and prepared the air supply engine to pump oxygen into their headgear. The two divers descended the vertical iron ladder attached to the Hayabusa Maru's side, their octopus-like rounded helmets swaying as they dragged lifelines, rubber air hoses, and coiled telephone lines down into the frigid water.

On the ship, among the captain, steamship company personnel, and Mr. Miyata—the leader of the salvage operation—Kenkichi and Kobayashi stood watching intently as the divers, their peculiar forms sinking into the sea.

The two divers held iron rods for prying things open in their right hands, while underwater lamps to illuminate the dark interior of the sunken ship dangled from their left hands. Using the force of large lead weights attached to their soles and chests, the divers sank steadily into the water. As they descended deeper, the huge hull of the ship came into view below. Having been submerged for twenty years, debris had accumulated in the water where seaweed grew and shells densely covered every surface—the iron vessel now resembled a massive undersea rock formation more than a ship. The hull lay sunken at a thirty-degree tilt. The deck sloped like a steep hillside. The two divers had descended near the bow of the wreck. They reached the bow's outer plating, scraped off encrusted shells with their rods, swung their lamps across the surface, and searched for markings of the ship's name. Without difficulty, they confirmed it was unmistakably the Taiyōmaru.

Then, the two of them clambered up the tilted deck in search of the hatch—an entrance leading from the deck into the ship's interior. Having soon found it, they descended a narrow staircase from there and entered the lower cabin. The iron staircase too was entirely covered in shells, giving them the sensation of entering a rocky cavern.

At the bottom of the stairs lay a spacious room. No—rather than a room, it was a large cave. The tilted floor held twenty years' accumulated debris, from which chest-high kelp-like seaweed grew so thickly that walking became nearly impossible. This area below the upper deck housed valuables like the strongroom—the very reason the divers had descended—but shells completely covered the walls, making it impossible to tell where the door might be. There was no hope of finding the gold ingots' location.

Since the cabin floor was also tilted at thirty degrees, every time they walked in their lead-weighted shoes, they slid and slipped. However, unlike on land, even if they slipped, they wouldn’t fall. This was because their bodies had become lighter in the water. When their feet slipped, the debris that had accumulated ten centimeters deep around the seaweed roots would billow up before their eyes, obscuring their view. Also, fish that had been hiding among the seaweed fled in a school. When that passed through the light of the underwater lamp, their scales shone gold and silver, creating a truly beautiful sight.

The divers wore rubber diving suits up to their wrists, but on their fingers, they had work gloves. That was because it made their work easier. One of the divers slipped on the tilted floor and plunged his hands into the sludgy debris. Then, his hand touched something strange and hard. “Hey, it’s Buddha!” If they were on land, they could have said that and alerted their companion, but in diving suits, they couldn’t even speak to each other. He swung the underwater lamp two or three times to the side and signaled for his companion to look this way. Then, he picked up the hard object from the debris and lifted it in front of the lamp.

It was the skull of a skeleton. With black hollows like caves for eyes and a row of long clenched teeth—though the divers were accustomed to skeletons in sunken ships, this one still felt eerie. Then, the other diver thrust his hand into the lamplight. There it was—gripping the skeleton’s leg bone. When they brought the underwater lamp closer to the debris on the floor and searched around, hands, feet, and rib bones began emerging one after another. The crew members of the Taiyōmaru had died in this room. Now they lay reduced to nothing but scattered bones.

"A monster! A monster!"

The two divers found the skeletal remains unsettling, but they weren’t frightened enough to be scared. They were strong and hardy young men—not the sort to be startled by trivial matters.

However, an incident occurred where even those courageous divers began trembling violently from sheer terror.

After the two had found the skeletal remains and were still attempting to proceed deeper, they noticed that the seaweed in the distance, faintly illuminated by their underwater lamp, was swaying back and forth. Though the seaweed around them had swayed with their every movement until now, it was strange for vegetation so far away to be moving. Could there be some large fish hiding there? That part of the sea was home to some truly enormous fish. Moreover, astonishingly giant crabs also inhabited those waters. The two divers, half in amused anticipation of what might leap out from behind the seaweed, approached the area while shining their underwater lamps.

Looking closer, from between the swaying kelp-like seaweed, something blackish slithered out. It might be a crab’s leg. Even so, it was an incredibly large and thick leg.

The blackish leg-like thing had split into several branches at the tip and curved sharply. Each one had something like sharp claws attached. They were exactly like human fingers. However, could there be such black human fingers? The divers stood frozen there. They had somehow become frightened. The black arm stretched out forcefully, revealing a black shoulder, and then a face-like thing peeked into view.

When they saw this, they let out an “Ah!” inside their diving helmets. Two large eyes glowing phosphorescent blue, a terrifying mouth split open to the ears with two white fangs jutting out sharply. And atop its iron-black head were sharp, pointed serrations like a crest. The divers had never actually seen the Iron Mermaid before. But they’d heard stories about it lying on the Hayabusa Maru’s deck. This had to be that Iron Mermaid. The monster had indeed followed the Hayabusa Maru all the way to Shionomisaki. And now it had already infiltrated the Taiyōmaru’s cabin.

Just as the divers, trembling violently, were about to flee, the monster revealed its entire body and suddenly leapt at them. Ah, the horror of it! It was like a locomotive charging forward in a movie.

Two glowing blue eyes and white fangs came charging through the water as if leaping at them.

“A mermaid!! The Iron Mermaid!! Pull us up! Hurry, pull us up!!” The divers shouted at the top of their voices inside their helmets. Their voices were transmitted through the telephone line to the Hayabusa Maru above. Then, desperately floundering, they tried to escape from the ship’s cabin. The monster reached out its terrifying hand from behind them, closing in on them. The diver who lagged behind had his leg seized in an instant. Five sharp talons dug forcefully into the diving suit.

He was fighting for his life now. He raised the iron rod in his right hand, wildly striking the monster, struggling and thrashing until he finally managed to free his leg. And both of them succeeded in rising from the ship's cabin to the hatch. For some reason, the monster didn't pursue them beyond that point.

Fish-shaped submarine When the divers returned to the Hayabusa Maru and reported the monster, the ship erupted into an uproar. Mr. Miyata and the other key figures hurriedly gathered in the captain’s cabin and began discussions.

“So it did follow this ship after all.” “It must intend to steal the gold ingots, of course.” “We must find a way to prevent it.”

Mr. Miyata said worriedly, his face pale. Then, the captain nodded and,

“Such a monster is beyond our capabilities to handle. Depending on the circumstances, we may have to request assistance from the Maritime Self-Defense Force. There’s no other way but to fire cannons into the sea and kill it. In any case, I will consult headquarters via wireless. And we’ll have a support team sent from Osaka.”

Then, the salvage company engineer who had been sitting there opened his mouth. “Even so, it’s taking time, isn’t it? “The monster may have already located the gold ingots, you know.” “And if they’re stolen... Captain, how about trying that?” “The diving bell?” “That’s right.” “I’ll go inside it and keep watch over the monster.” “No matter how powerful this Iron Mermaid might be...”

“Hmm, I suppose there’s no other choice. Then, you’ll be the one to go in?”

A Diving Bell was a large spherical submersible made of thick iron. A person would enter it and sink to the seabed.

The iron sphere had thick glass windows, with powerful underwater lamps resembling searchlights mounted above them, providing a clear view of the sea. Moreover, the iron sphere had two iron arms, their ends forming large pincers for grasping objects. Iron pincers. The salvage company used this submersible for deep-sea work at depths where divers couldn’t reach, but the captain had brought the machine aboard the ship as a contingency measure.

The Hayabusa Maru was equipped with a small crane for handling heavy submersibles. Several crew members operated the crane, hoisted the submersible from the ship’s hold with a wire rope, and the engineer entered it. After sealing the machine, they swiveled the crane toward the sea surface and began slowly lowering the submersible into the water. The interior of the submersible was designed so that one could operate everything while seated, much like an airplane cockpit. Before the seat lay numerous buttons; pressing them allowed free control of the external iron arms and claws.

The engineer stared intently into the sea through the glass porthole. The submersible steadily descended. Under the strong light from the lamp above the window, visibility extended clearly up to ten meters ahead. Within that illuminated sphere, fish of all sizes darted left and right, creating a truly beautiful spectacle. The submersible wouldn't enter the sunken ship's hatch itself, instead positioning near the hatch entrance to maintain surveillance.

As he watched from the window, the sunken ship on the seabed gradually grew larger. In other words, they were moving closer to it. "What an enormous fish!" The engineer muttered involuntarily. From beyond the reach of the electric light, he had seen a massive fish—something akin to a baby whale—approaching their position. While whales weren't unheard of in these waters, this was clearly no ordinary whale. What struck him as odd were its terrifyingly large eyes that glowed intensely like car headlights. The eyes resembled those of a minnow, yet its body measured tens of thousands of times larger than one. Could such a bizarre fish truly exist?

As he was pondering this, the giant fish gradually drew closer. Not only were its eyes enormous, but its mouth was perfectly round like a May carp streamer. And its mouth didn’t move at all. The light from its eyes grew increasingly intense. The water ahead was suddenly illuminated as if by a searchlight. Attached to the giant fish’s back was something like a transparent air bladder. It was a flat sack.

“Wh-what... That’s not a fish! It’s a submarine! A fish-shaped submarine!” The engineer involuntarily let out a shrill shout. It was made of iron. What had appeared to be two eyes were actually the submarine’s headlights. That round mouth might actually be the muzzle of a cannon. Even so—where on earth could this bizarre submarine have come from? No… It wasn’t from any country at all. This must surely have come straight from hell itself.

The Great Underwater Struggle

“Oh! There’s something strange here. What on earth is that?”

The engineer started and stared at the submarine’s back. The glare from the two front-mounted lights was so intense that the back remained poorly visible, but there—crouching in that obscured area—was something horrifying. It was the Iron Mermaid. Its iron face bore an iron crest, with two fangs protruding sharply from a mouth split open to the ears, and its body was that of a crocodile-like monster. That thing was clinging gecko-like to the back of the fish-shaped submarine, its glowing blue eyes fixed in a piercing stare in his direction.

Since the engineer was inside an iron sphere, he was safe no matter what monster approached. However, the terrifying appearance of the Iron Mermaid made him shudder, and his body froze stiff.

The fish-shaped submarine was now right before their eyes. While they could move freely, the submersible was suspended by a rope from the Hayabusa Maru, making escape impossible. The engineer grabbed the telephone inside the submersible and shouted.

“Hurry up and pull me up… There’s a terrifying submarine here! On its back… the Iron Mermaid is riding!” “What? A submarine?” came the Hayabusa Maru captain’s reply. “Is that true?!” “Yes! It’s shaped like a fish—a horrible submarine! It’s right in front of me now! Dangerous! Hurry, hurry! Pull me up!” Aboard the Hayabusa Maru, they apparently began the retrieval operation, and the submersible started gradually rising upward.

At that moment, something startling occurred.

Before their eyes, from a hole resembling the round mouth of the fish-shaped submarine, a long black rod like a snake’s tongue abruptly shot out. The tip of the rod was split into two, forming what appeared to be a gripping mechanism. And then, that claw extended toward the upper part of the submersible carrying the engineer.

The engineer hurriedly peered through the small glass window open above. Ah! The monster's iron claw was trying to clamp down on the rope hoisting the submersible! "It's terrible! They're trying to cut the rope! Hurry! Pull me up faster—much faster!" Aboard the Hayabusa Maru, they spun the winch engine even faster. The force made the submersible lurch violently, nearly crashing into the fish-shaped submarine right above.

The engineer frantically spun the handles before him. Then, the iron arm protruding from the submersible jerked left and right with forceful motions, slamming against the submarine's flank. The Iron Mermaid clinging to the submarine's back thrust its neck toward them, glaring with phosphorus-glowing eyes.

The engineer clattered the handles again. The iron arm stretched toward the monster and nearly seized its crocodile-like tail.

It was a terrifying clash between the submarine's iron tongue and the submersible's iron arm. It was a battle of machine versus machine. The seabed waters swirled into whirlpools and foamed, fish scattered in panic, the round iron submersible swayed wildly, the submarine thrashed its tail left and right to avoid releasing the rope, and the Iron Mermaid thrashed about on its back—the life-and-death struggle raged on. But in the end, the Hayabusa Maru's winch proved stronger than the iron claw's might. The wire rope was rapidly wound up, and the submersible shook off the iron claw to be hoisted toward the sea surface.

After exiting the submersible and boarding the deck of the Hayabusa Maru, the engineer stood drenched in sweat, his face flushed crimson as droplets fell steadily from his brow. After catching his breath, he recounted every detail of the underwater battle to the captain and Kenkichi's father. "I never imagined they'd have a submarine," he said. "The Iron Mermaid has allies down there." "We can't possibly match them like this." "While we're stuck with this clumsy submersible, they've got submarines darting across the seafloor." "I suppose we'll finally have no choice but to deploy depth charges."

They had no choice but to request support from the Maritime Self-Defense Force. The captain sent a wireless message to the Osaka branch and informed them of the situation. In response, a wireless message came back from the branch office—one that astonished everyone.

“DETECTIVE AKECHI DEPARTED THIS MORNING WITH POWERFUL WEAPONS. SHOULD ARRIVE THERE AT 5:00 PM.”

Ah, Detective Akechi was coming. Moreover, he was coming with powerful weapons. The people danced for joy and involuntarily shouted "Banzai!"

Detective Akechi was coming.

Speaking of 5:00 PM, that was still over an hour away. Everyone remained standing motionless on the deck, waiting for the ship carrying Akechi to arrive.

“What on earth could these ‘powerful weapons’ be?” “Even a famous detective couldn’t have known about their fish-shaped submarine. I’m worried whether he’s bringing anything that can defeat that thing.” The captain whispered these concerns to the engineer. Even when they radioed for details about the weapons, they received no answers.

Over here，the boys，Kobayashi and Kenkichi，were talking with bright expressions.

“Kobayashi, that’s Detective Akechi for you! When you sent that wireless message from this ship yesterday informing him about the Iron Mermaid’s pursuit, he immediately headed to Osaka, didn’t he? He must have taken a plane. And he departed from Osaka Port early this morning, didn’t he? But still—what could these ‘powerful weapons’ be?” “I don’t know either. Detective Akechi is always thinking much further ahead than us. So when he took on this case, he might have already properly prepared the weapons. It’s alright now. If Detective Akechi comes, it’s as good as done!”

Kobayashi said happily, smiling brightly.

Before long, a wisp of smoke became visible beyond the distant horizon. When they peered through binoculars, the small figure of a white steamship appeared there. It was the Kamome Maru—an express vessel from the merchant shipping company. This regular passenger ship passed Cape Shionomisaki, but since it was a high-speed vessel, they had learned through wireless message that Akechi was aboard. The Kamome Maru, its hull painted pure white, rapidly grew larger as it approached. The people on Hayabusa Maru's deck waved handkerchiefs, shouted "Banzai!", and welcomed it.

The beautiful Kamome Maru came to a stop about fifty meters away on the sea surface, and a boat was being lowered. On the opposite deck as well, passengers were crowded together, watching this side. They must have heard the rumors about the gold ingot salvage.

The lowered boat, with four sailors rowing the oars, approached straight toward them. Cheers of "Banzai!" swelled across the deck of the Hayabusa Maru.

Standing tall in the boat was our renowned detective, Akechi Kogorou. His tall frame was clad in a well-fitted black suit, his tousled hair flowing in the wind as he raised his right hand high in greeting. “Huh? What is that?” “Something like a sea monster is coming!”

Someone shouted. When they looked, a large black monster was following the boat from the stern of the Kamome Maru and approaching. It was a black, whale-like creature with a massive hump on its back. Upon closer inspection, atop its hump stood what appeared to be a slender iron rod. Kobayashi shouted.

“Ken, that’s a periscope! It’s what lets you see above water from inside a submarine. So that means it’s a submarine! Wow, incredible! Our submarine’s here!” “You’re right. We’ll be safe now. That’ll destroy the enemy’s fish-shaped submarine! Hey Kobayashi, Detective Akechi’s amazing!”

The two boys jumped up in delight. The people on deck were also in an uproar upon hearing that their ally’s submarine had arrived. Once again, cheers of "Banzai, banzai!" welled up.

Before long, the boat pulled alongside the Hayabusa Maru, and Akechi climbed the iron ladder to appear on deck. Then, while holding onto Kobayashi’s shoulder as the boy clung to him, he exchanged greetings and shared reports with Kenkichi’s father, the captain, and the engineer. A large number of sailors formed a circle around them, their eyes fixed on the renowned detective.

“I see. Did the enemy also have a submarine? I hadn’t considered that far, but since I thought a submarine would be essential to defeat the Iron Mermaid, I had made preparations for it from the very beginning. Currently, Japan doesn’t have submarines like the ones the navy used in the past, but I learned that a small civilian-made submarine for undersea tours was stored at the Toyo Steamship Company, so I had it serviced and prepared to be operational at any time. Since it’s that type of submarine, it can’t launch torpedoes—but its shape resembles a navy submarine scaled down exactly. It’s more than enough to intimidate the enemy.”

“Since the submarine had been moved from Kobe to Osaka Bay, we had the Kamome Maru tow it here.”

After they had consulted for some time, Akechi proposed the following plan. "That submarine has two skilled pilots aboard. After thoroughly briefing them on their procedures, they'll submerge it near Taiyōmaru. Then they'll lure the enemy's fish-shaped submarine far away. They'll definitely keep it away from the Taiyōmaru for about thirty minutes. Our submarine has a wireless device installed, so we can receive moment-by-moment reports. During those thirty minutes, divers from this ship will dive down, search inside the Taiyōmaru, and locate the gold ingots. We can divide it into thirty-minute intervals and repeat this process as many times as needed."

Therefore, they ultimately decided to proceed with that method. After summoning the pilots and giving them detailed instructions, they submerged the submarine. At last, the battle between Akechi’s submarine and the enemy’s fish-shaped submarine was about to commence.

The Striped Monster

On the seabed where the Taiyōmaru lay sunken, the fish-shaped submarine glided smoothly through the water. On its back crouched the Iron Mermaid. The monster was likely issuing commands to its subordinates through the upper glass window of the submarine. It straddled the vessel like a general mounted upon a warhorse.

Suddenly, the water stirred, and from above, a large black thing swiftly descended. It was Akechi's submarine. Since this submarine was intended for sightseeing, it had thick glass windows at the front and on the sides. The light from the submarine’s interior lamps was spilling out through those windows. When viewed from afar, it looked like a monster with a third eye in an odd place. The Iron Mermaid noticed it and, seemingly startled, braced herself, glaring fixedly in that direction.

After submerging to the same depth as the fish-shaped submarine, it came to a stop and abruptly began flickering its interior lights on and off rapidly. Each time, the three glass windows would darken and brighten, as if blinking.

This was emitting Morse code signals using light, exactly as Detective Akechi had instructed. They were using light to transmit those telegraphic Morse code signals—the rhythmic *dot-dot-dash* pulses. They were testing this under the assumption that even among the monster gang, there must be someone who could understand Morse code.

Then, the two eyes of the fish-shaped submarine began flickering rapidly. This was their answer: they understood Morse code. Therefore, they transmitted the genuine message. “Evacuate this area immediately. If you refuse, we will launch torpedoes.”

We didn't have any torpedoes aboard our submarine，but given its identical shape to naval submarines，the mere claim was certain to startle the enemy. True to expectations，the fish-shaped submarine began moving. It withdrew from beside the Taiyōmaru，fleeing toward some unknown destination.

They immediately gave chase. The two small submarines were in a seabed race. The three-eyed monster chased the two-eyed small whale along its path - seawater churned violently, submerged rocks were flung aside, long seaweed thrashed about as if battered by a storm - creating a fearsome underwater pursuit across the seabed.

Akechi's submarine was ultimately designed for sightseeing purposes and lacked such speed. Unfortunately, it couldn't match the fish-shaped submarine's velocity. Gradually, the distance between them only grew wider. After pursuing them for about five minutes, they lost sight of their target. The enemy had switched off their twin headlights that resembled glowing eyes. Then, blending into the seabed's darkness, they disappeared completely. The pilots felt as if their adversaries had been wiped away in an instant. It seemed like some sort of ninjutsu had been employed. Nevertheless, having driven off the enemy, all that remained was to circle around the Taiyōmaru while maintaining watch. Accordingly, they sent a wireless message to Detective Akechi aboard the Hayabusa Maru.

“Enemy submarine and Iron Mermaid have fled. True target is naval district. Send divers immediately.”

Upon receiving the wireless message, the Hayabusa Maru immediately sent down a diver who had been properly prepared to the Taiyōmaru. He was their most skilled diver.

The diver, holding an iron rod in his right hand and an underwater lamp in his left, descended through the hatch into the ship compartment he had entered once before. Since the Iron Mermaid had fled, there was nothing left to fear. All he needed to do now was locate the gold ingots. Swinging his underwater lamp to illuminate the area as he looked around the spacious ship compartment, he noticed a large square hole in one of the walls. "Huh?" he thought. When he looked closer, though it was covered in so many shells that he couldn’t make it out clearly, there was indeed a door there—and it stood open.

It couldn't have opened by itself. Someone had come before him and opened the door. When the diver reached that conclusion, he froze in shock. The Iron Mermaid shouldn't have been there anymore. Then who had opened it?

Or perhaps those monster gang members had opened this place and long since stolen away the gold ingots? In any case, this was a major crisis. He brandished his lamp and cautiously peered through the doorway to verify this.

Then, inside the small room, there was something glowing dimly. An underwater lamp was lying on the floor of the room. He gasped and looked closer—oh, there was an eerily strange creature squirming right there! It was shaped like a human. However, it was no ordinary human. Its entire body was covered in thick pitch-black stripes. It was a black-and-white striped monster. There are sea breams with beautiful stripes. It was a black-and-white striped monster identical to those.

Its face was human, but it was a terrifying creature that looked just like a gorilla. Its face glistened as if covered with glass, and on the back of its head sat something like a pitch-black jagged crest. At the tips of its feet were large, seal-like flippers.

The monster, holding a wooden box under its arm, abruptly turned toward him. Along the wall behind it, similar wooden boxes were stacked in a low pile.

“Ah, I see. The gold ingots were here all along! They were put into these wooden boxes and stacked here all along.” The diver realized it in an instant. The striped monster was indeed the gold ingot thief. The diver yelled into the telephone inside his diving helmet.

“I’ve found the gold ingot thief! “It’s the striped monster! “I’ll catch it! “Please send backup immediately.”

Having done that, he suddenly lunged at the striped monster.

Monster Crab In the deep water, he couldn’t lunge forward abruptly. He floated gently, as if swimming, and grappled with his opponent. When the striped monster saw this, it panicked and tried to drop the box of gold ingots to flee, but it was already too late. And so began the terrifying grapple between the striped monster and the diver who resembled a ghostly knight in Western armor.

Though not to the extent of the outer room, this room too had accumulated twenty years' worth of ocean debris. As the two grappled, the debris swirled upward, and the area became as though enveloped in smoke.

Because the Striped Monster kept trying to break free, the two of them—locked in their grapple—had somehow moved outside the door and reached the base of the iron staircase leading up to the deck.

In that area, kelp-like seagrasses with large leaves grew in abundance. Fish that had lagged behind were also swimming there. Amidst this, the armored ghost and the striped monster tumbled sideways, flipped upside down, and grappled with each other. Unlike fights on land, the underwater grappling was slow and eerily uncanny, like something out of a slow-motion film.

When they reached the base of the stairs, the striped monster suddenly surged with renewed vigor. As it thrashed wildly like a fish, the diver's grip slipped loose from his opponent. Then, using the large flippers on its feet to kick through the water with a sharp swish, the monster swiftly ascended the staircase. The diver, weighed down by his heavy lead-lined boots, stood no chance of matching its speed. His only option was to laboriously climb each step one at a time. To his bitter frustration, he'd ultimately allowed his quarry to escape.

The diver hurriedly returned to the original cabin, grabbed an underwater lamp, and ascended to the deck.

Then, on the seabed a short distance from the Taiyōmaru's massive hull, a white light could be seen moving swiftly away into the distance. It was an underwater lamp. Since the monster had fled without an underwater lamp, that couldn't be it. What on earth could that be?

“Ah, I see. My friend had come diving after me. And he’d found the monster and was chasing it.”

The diver had thought this through, so he hurriedly moved closer in that direction. Since he had earlier requested backup from the *Hayabusa Maru* via the telephone in his diving helmet, another diver had descended. With no lamp to guide it, the monster lost all sense of direction. While floundering through the kelp forest, it found itself trapped between two divers. The underwater lamps closed in rapidly from both sides like glowing monster eyes.

The monster barely managed to escape the kelp forest and fled across the jagged, rocky seabed. The two divers were chasing it from about five meters behind. The figure of the Striped Monster hid in the shadow of a large rock. The two divers hurried there, but they couldn’t run as fast as they could on land. When they finally reached the shadow of the rock and looked, there was nothing there anymore.

Wondering where it had gone, they swung their underwater lamps around, peering through the murk in all directions, but found no trace of the enemy anywhere. There was no way it could have gotten far in such a short time. Yet aside from this massive rock formation, there were no conceivable hiding places. The two divers gestured in bafflement—a silent "What the—?!"—and exchanged uneasy glances through their diving helmets.

As the two continued searching the area, they noticed something squirming at the base of the large rock. The bluish-black rock was squirming. The two were startled and directed their underwater lamps toward it. No, it wasn't a rock. Something large—indistinguishable from a rock yet unidentifiable—had separated from the base of the stone and was moving toward them.

“Ah, it’s a crab!”

One of the divers inadvertently shouted inside his helmet, and his voice blared shrilly through the Hayabusa Maru’s receiver.

What had appeared to be a rock was a giant crab. It was a terrifying crab twice the size of a human. It came scuttling forward on eight legs, lifting its massive pincers—each nearly a meter long—opening and closing them with a forceful grip. White eyeballs the size of rubber balls protruded smoothly. It approached while rolling those eyeballs around.

A scream like "Waaah!" echoed doubly through the Hayabusa Maru's receiver. The two divers screamed in unison. And then they suddenly began to flee.

The Monster Crab chased the fleeing divers for five to six meters, but then, for some reason, turned around and began moving away into the distance. And then, as if melting into the darkness, it disappeared from view.

The two divers immediately used the telephone in their diving helmets to request to be pulled up. When they returned to the deck of the *Hayabusa Maru* and were surrounded by everyone, they explained the underwater events in detail. However, upon hearing this, Detective Akechi tilted his head slightly and said:

“Such a large crab shouldn’t exist in these waters. It might be some trickery by the villains. They could have put on crab disguises and escaped. Those disguises might be made of thin metal or vinyl. And they might have folded them up small and hidden them inside a hole in the rock.” “Huh? So were the gold thieves inside that crab?”

One of the divers exclaimed in surprise. “I’m afraid that’s the only possible conclusion,” Detective Akechi replied. “Disappearing while hidden in rock shadows isn’t something humans can achieve. These gold-thieving fiends are magicians through and through. They’ve finally shown their true colors.” A mischievous glint appeared in his eyes as he added, “This grows intriguing. For my part, I find no satisfaction unless facing such sorcerous adversaries.” The renowned detective ran his fingers through his disheveled hair and smiled faintly.

Scattering Gold Ingots

By then, the western sky was already dyed crimson with sunset clouds. The sun was visibly sinking. Before long, the eastern sky grew pitch black, the darkness spread westward, and finally night fell.

However, if the enemy had discovered the location of the gold ingots, they couldn’t afford to rest just because it was nighttime. Detective Akechi, the captain, Mr. Miyata (Kenkichi’s father), and others huddled together to discuss their plans. And so, they decided that even at night, they would use a large-scale mechanism to hoist up all the gold ingots at once. The *Hayabusa Maru* had prepared a large net-like contraption made of thick iron chains. It was a device for hoisting heavy cargo.

The plan was to attach wire ropes to it, lower it to the seabed with a crane, place the boxes of gold ingots into the iron chain net, and hoist them up.

Once that was decided, they radioed the submarine monitoring the enemy's fish-shaped submarine to surface once. After making thorough preparations, they would submerge again along with the iron net and have it keep watch until the hoisting was completed. They decided that three divers would accompany the iron net, but since that alone wasn’t sufficient for reassurance, they also had the giant iron sphere—the diving machine—submerge to the seabed together with them, where it would keep watch outside the Taiyōmaru’s deck hatch.

While all the crew members were working together on these preparations, Kobayashi clung to Detective Akechi and pleaded earnestly. “Hey, Detective, please let me ride in the diving machine. “Pretending to be a diver is something a kid like me can’t possibly do, but the diving machine should be fine. “I can just ride in front of the engineer. “There’s enough space for that. “Hey, Detective, please let me!”

Detective Akechi loved Kobayashi as if he were his own child, so when begged so persistently, he couldn't bring himself to refuse. With a wry smile, he consulted the engineer.

Then, the engineer also smiled warmly, “If you want to ride that badly, you can come along.” “It might be a bit cramped, but for someone as small as Kobayashi-kun, it shouldn’t be impossible to ride.” “Having cute Kobayashi-kun with me will make it more enjoyable.”

he agreed.

“Kobayashi, are you going to ride in the diving machine?” “I wish I could ride too.”

Kenkichi said enviously. "Your father would never permit it." "You're smaller than me and not accustomed to adventures yet." "But first, if I test it and it's safe, you should ride next time." With those words, Kobayashi comforted Kenkichi.

In about thirty minutes, all preparations were completed. First, the submarine sank and began patrolling around the Taiyōmaru. Next, the diving machine submerged. Finally, the iron net and three divers sank down.

Young Kobayashi was overjoyed. Perched on the engineer’s knee, he made himself small as he peered intently through the front glass window.

The diving machine was equipped with a powerful electric light resembling a train’s headlight, so the depths of the night sea remained clearly visible.

Fish swam outside the window. Translucent jellyfish resembling strips of agar drifted ethereally. They rose smoothly upward. In other words, the iron sphere of the diving machine steadily descended. It felt exactly like riding an elevator. “Look, that’s the Taiyōmaru. It’s huge, right?” At the engineer’s words, he looked down to see a massive hull covered entirely in barnacles lying sprawled out. It smoothly approached, and the diving machine came to a stop near the hatch on the Taiyōmaru’s slanting deck.

In the distance, something glowing like an eyeball passed smoothly by.

"What's that?" "It looks like a car's headlight." "That's our patrol submarine." "It circles round and round the Taiyōmaru." "The enemy's fish-shaped sub could surface anytime."

Before long, something strange descended smoothly from above—not from the air, but from the upper reaches of the sea. It was the iron net and the three divers attached to it. The iron net was lowered right beside the deck hatch, and the three divers waved their underwater lamps, signaling a greeting toward the diving machine as they descended one after another into the hatch. After they descended, three ropes and an air hose swayed gently like long wisteria vines. Before long, one of the ropes snapped taut—pulled upward from above—and a diver emerged from the hatch clutching a square wooden box. And he placed the box into the iron net. After putting it in, he returned into the hatch.

Then the next diver appeared, placed a similar box into the iron net, and returned. In this manner—one diver after another—the three divers kept emerging from and reentering the hatch until, gradually, the number of boxes inside the iron net increased. There were thirty boxes of gold ingots in total, but since it was impossible to handle them all at once, they decided to put half—fifteen boxes—into the iron net, had the divers notify via telephone, and then hoist it up.

The iron net, swollen with fifteen boxes, was being hoisted up swaying gently as the thick iron rope suspending it pulled taut. The three divers stood on the slanted deck, looking up at it.

However, just as the iron net was raised about ten meters. One of the divers jumped up in a strange pose and pointed with both hands toward the top of the iron net. Then, the remaining two divers also raised their hands in the same manner and began dancing like madmen.

“Oh, something’s wrong.” “Hello? Raise the diving machine about twelve meters.” "It seems something's wrong with the iron net's rope." “Quickly, please raise it.”

The engineer shouted into the telephone.

The diving machine jolted and began rising smoothly upward. Pushing past the iron net, it reached the rope. "Please hoist both the iron net and diving machine at matching speeds."

After relaying instructions over the phone, he moved the front handle, causing the diving machine's window to turn toward the rope as a powerful electric beam illuminated the spot. "Ah! A crab! There's a crab clinging to the rope!"

Kobayashi-kun involuntarily shouted. It was that monster crab—twice the size of a human. It clung to the iron net’s rope and was fumbling around with something. “Oh no! This is bad!” “That bastard’s trying to cut the rope!” “It’s moving a huge file back and forth like a saw!” This time, the engineer shouted. And he pressed back to the telephone, “Hello? Please move the diving machine closer to the iron net.” “There’s a bastard trying to cut the rope!” “We’ll attack with the iron claw.”

Smoothly, it approached the rope. A giant crab was squirming right before their very eyes.

“It’s time for battle! Watch this. Just wait and see—I’ll take down that thing with the iron claw soon enough.” The engineer shouted boldly and gripped the front handle. With a metallic screech, the giant iron shears attached to the diving machine’s side began to move.

The crab’s back was right there in front of them. The iron claw extended smoothly toward it. However, since the diving machine itself hung suspended from above, they couldn’t maneuver it as they intended. It was just one breath away from reaching it, yet couldn’t quite reach it.

“Closer! Bring it closer! More! More!” Shouting into the telephone, the engineer ground his teeth and worked the handle. “Ah! It reached! Got it!”

When he cranked the handle with a clank, the iron claw clamped down firmly. The claw seized two of the crab’s legs and wrenched them off with a violent tug. Yet the opponent showed no reaction. Losing two of its artificial limbs meant nothing to the construct. The file’s sawing intensified until its metallic screech seemed to reverberate inside the diving machine itself. Both the iron net and diving bell were now being hauled upward at maximum speed.

They intended to haul it up before the rope snapped. They were now only about ten meters from the Hayabusa Maru. They were just one breath away.

But, oh, at that moment. Finally, the rope snapped. The Monster Crab detached from the rope and smoothly vanished into the distance.

The iron net plunged downward with terrifying force. The net spread out as fifteen boxes scattered haphazardly while falling. Some collided with the Taiyōmaru's deck while others crashed into seabed rocks. The rotten wooden boxes shattered upon impact, sending glittering gold ingots scattering in every direction.

Kenkichi's Peril

When they realized this, the Hayabusa Maru broke into an uproar. They immediately decided to send five divers down to collect the gold ingots, but preparing five men to submerge required various arrangements. Moreover, since it was pitch-dark night, the work became even more difficult. On the deck of the Hayabusa Maru, numerous bright electric lights hung suspended, and beneath them, a great many crew members dashed left and right preparing for the dive.

Kenkichi had been watching the busy scene beside his father, but when he headed toward the hatch leading down to his cabin for an errand, he noticed a sailor on the dark deck opposite urgently gesturing. The ship's important figures and crew members had all gathered on one side of the vessel, working to lower the divers. The electric lights were concentrated in that area alone, leaving the other decks pitch black. A sailor was beckoning from the pitch-black deck, which struck Kenkichi as odd.

“What is it?”

When he asked, the sailor smiled and,

“Mr.Kobayashi is waiting over there.I was told to come get you，young master，”he replied.The“Mr.Kobayashi”in question was，of course，none other than Kobayashi，the boy assistant of Detective Akechi.Kobayashi，the boy，had been inside the round iron diving machine that sank to the seabed，but just a while ago，the diving machine had been retrieved，and he should have come out of it and been resting in his own room．Why would he be summoning Kenkichi now？

“Where is Mr. Kobayashi?” When Kenkichi asked again, the sailor pointed toward the stern and,

“Over there. “He says there’s urgent business with you, young master.” The sailor replied and walked toward the eerily pitch-dark stern. Kenkichi thought it strange, but never imagining enemies could be aboard the *Hayabusa Maru*—and since Leader Kobayashi of the Boy Detectives Club was summoning him—he couldn’t defy orders as a member. Before he knew it, he’d absentmindedly followed the sailor.

The stern deck was eerily pitch-dark. Even when straining his eyes，he couldn't make out anything resembling a human figure. "Where is Mr.Kobayashi?" "There's no one here!" Feeling a bit frightened，as he said this，the sailor—

“Look, there it is—on the other side of that barrel.”

With that, he took Kenkichi’s hand.

When he looked, about three meters ahead, there was something like a large beer barrel placed there. It was a much larger one than an ordinary beer barrel.

Wondering what Mr. Kobayashi could possibly be doing behind a barrel, he hurried over—but when he looked behind it, there was no one there. Since the barrel’s lid had been removed, he peered inside thinking someone might be hiding there—but the barrel was completely empty, containing neither sake nor water. “H-hey, what are you doing…?” Just as he tried to speak, a large hand clamped forcefully over Kenkichi’s mouth. Even as he struggled, another hand was holding his body tight, leaving him unable to do anything.

The sailor lifted Kenkichi up and effortlessly shoved him into the large barrel. After closing the lid from above, he pulled nails and a hammer from his pocket and began pounding them in with steady blows. It all happened in an instant. All the ship’s crew were gathered around the diving operations, so no one had noticed. Even so, who on earth was this sailor? What could they possibly intend by stuffing Kenkichi into a barrel?

Could it be that this sailor was an infiltrator from the Iron Mermaid's band of fiends? Had they boarded the Hayabusa Maru disguised as crew members when it departed Osaka?

The sailor wound the long rope that had been left there around the barrel, tied it tightly, then lifted the barrel and carried it to the edge of the stern. And he stared fixedly down at the dark sea.

At that moment, something flashed on the sea surface thirty meters away from the Hayabusa Maru. A round, glass-like object floated on the water, its interior suddenly illuminated by an electric light. The light vanished as quickly as it appeared, but he immediately recognized what it was. This was none other than that fearsome fish-shaped submarine. The whale-like black hull had surfaced halfway, its round glass protrusion glowing faintly from within. There could be no doubt - it had just signaled to their accomplice aboard the Hayabusa Maru.

Then, a truly terrifying thing occurred. The sailor gripped the rope with both hands and lowered the barrel containing Kenkichi-kun from the ship's side to the sea surface. The barrel floated swaying gently on the surging waves. The sailor took off his coat, stripped down to a shirt, threaded one end of a long rope through the stern railing, gripped it, and descended toward the sea surface himself. Then, treading water, he hauled in the rope fastened to the railing, wrapped it around his body, and began swimming quietly. Needless to say, he was heading toward the fish-shaped submarine.

As the sailor swam, the barrel connected by the rope was pulled along in that direction. And in no time, they drew near the fish-shaped submarine.

Then, as if waiting for this exact moment, the circular glass panel on the submarine's back suddenly flipped upward, revealing a human face emerging from within.

“Did it go through?”

“Yeah, the kid’s in the barrel. Tie this rope to the tail end.” The sailor in the sea answered thus, climbed onto the fish-shaped submarine, and slipped inside through the glass-hatched entrance.

Then, the man who had been inside emerged on the fish-shaped submarine’s back in his place, took hold of the rope’s end, and ran toward the vessel’s tail. After a short while, that man returned.

“I tied it securely. There—now it’s secure.”

With that, he slid into the dorsal entrance of the fish-shaped submarine. The round glass lid snapped shut with a clack, and the vessel quietly sank into the sea.

All that remained was the barrel, pulled by the rope, bobbing gently on the waves.

The Cave’s Uncanny Phenomenon

The boy Kenkichi, stuffed into the barrel, had been so shocked that he seemed to lose consciousness for a while, but before long realized that his barrel was swaying violently through some tremendous motion. I must have been thrown into the sea. And now I drift at its mercy. The realization struck him. What a desolate fate this was. With not even a sliver of space in this barrel - no one could hear him cry or scream however loudly he tried.

“Dad! Mom! Mr. Kobayashi!” “Mr. Kobayashiii!” Even though he knew they couldn’t hear him, the cries kept spilling from his lips unbidden. Kenkichi-kun shouted over and over at the top of his voice.

After some time, he suddenly noticed that the way the barrel was shaking had changed. Until now, it had been drifting gently, but now he felt it suddenly start rushing in one direction. It was overcoming the waves and advancing with terrifying force. It felt as if I were being pulled by a speedboat moving at an incredible pace.

As it was pulled along, the barrel spun around and around. Kenkichi-kun’s body kept spinning ceaselessly—now facing upward, now sideways. Every time he spun, some part of him collided with the barrel walls, and the agony was beyond words.

Kenkichi-kun thought it would be better to die quickly than endure such agony.

Before long, not only was his body being jolted violently, but he also began struggling to breathe. Since it was a barrel sealed so tightly that not even water could seep in, the air inside had grown foul. In other words, the oxygen had diminished, making it hard to breathe. If I stay in this barrel much longer, I’ll surely die.

After that, he had no idea how much time had passed—he was in a daze. When he suddenly came to his senses, the barrel had stopped moving entirely. The violent shaking that had been rocking him ceased completely, leaving his ears ringing with an eerie silence so profound it felt unsettling. Then the barrel moved smoothly again—as if being lifted—and swayed gently, but this felt different from floating on waves.

Then, just as he heard a terrifying BANG, BANG near his head, a rush of cold air whooshed in. The lid of the barrel had been opened. When Kenkichi-kun inhaled that air, he found it truly sweet. I had never dreamed air could taste this sweet. Someone lifted Kenkichi-kun up and took him out of the barrel. When he looked, it was the thug sailor from earlier, though his clothes were different.

But what surprised him more was where he now found himself. It was a cave-like place in the mountains. It had the feel of an uneven, tunnel-like passage through blackish rock. Kenkichi-kun wondered if he had been taken into a thieves' den. There was, of course, no way to escape. Beside him stood the thug sailor keeping watch, and moreover, his body had been worn out completely—he no longer had the energy to do anything. Kenkichi-kun crouched beside the barrel and could only blankly gaze around.

That was when it happened. From the far side of the cave that had become like a deep tunnel, something strange flickered into view. Because it was inside a dimly lit cave, he couldn't make it out clearly - but there was something about it that made his blood run cold, both startling and terrifying.

As he stared in shock, the figure of that strange creature slid out from behind a rocky corner. Kenkichi-kun let out a cry and involuntarily tried to flee. Then, the sailor grabbed Kenkichi-kun’s shoulder with terrifying strength and forced him back down into a seated position.

“Ufufufu, I’ve no intention of devouring you,” the Iron Mermaid mocked, its metallic voice grating like rusted gears. “Just stay put. Those others have urgent business to attend to—they’re heading out now.” The creature fully emerged from the shadows, drawing nearer with mechanical precision. This was the dreaded Iron Mermaid in its horrific entirety—a human-sized abomination armored in iron scales. Jagged crests like steel cockscombs ran from skull to spine, glowing azure eyes piercing the gloom. Its maw split ear-to-ear, twin fangs glinting coldly as they slid into view.

The monster clawed its way across the rocks with iron hands. It had a long, crocodile-like tail, but beneath that tail were short, leg-like appendages, and with its two arms and those legs, it crawled freely.

Kenkichi-kun pressed himself tightly against the rock wall, terrified as he watched the monster—but the creature paid him no mind, passing right before him and exiting the cave.

Then, once again, there was a sign of something moving in the depths of the cave. When he snapped to attention and looked in that direction, lo and behold, another Iron Mermaid—identical to the one that had just left—lumbered out from there.

No, not just one. One after another, the same monsters emerged in a steady stream, like a procession of Amazon River crocodiles. Kenchiki-kun was so overwhelmed that he couldn't even count them. In truth, eight Iron Mermaids passed before Kenkichi-kun and exited the cave. It felt like being trapped in a horrifying nightmare. I had thought there was only one Iron Mermaid, but so many had been hiding inside the cave. And they filed out to who-knows-where.

What in the world was going to happen? Could it be that those monsters had gone out to interfere with the Hayabusa Maru's gold ingot salvage operation? If all those monsters were to run wild in the sea, what in the world would become of things?

As Kenkichi-kun, having lost all capacity for thought, was staring blankly, the sailor poked his shoulder and,

“Come on, we’re heading deeper in. “The leader’s been waiting.”

said something strange. Who on earth was this “leader”? Kenkichi-kun remained led by the sailor as he walked over jagged rocks deeper into the cave. After proceeding through winding cave passages for some time, the space suddenly brightened. There, the cave widened into a rock-enclosed area resembling a room. An ornate carved table stood there, upon which rested a Western-style candlestick holding three burning candles.

Beside the table stood an equally large, carved chair, upon which sat a terrifying figure dressed entirely in black.

He wore a black velvet hood pulled completely over his head. Only the eye and mouth areas of the mask were cut out in triangular shapes, and from those holes, eerily glowing eyes stared fixedly in this direction. His body was clad in an equally black velvet garment that hung loosely like a cloak. This must be the "leader". “I’ve brought Miyata Kenkichi.” The sailor respectfully bowed and said.

“Yeah, well done. So you did pack him in a barrel after all.”

The pitch-black monster inquired in a thick, hoarse voice. “Yes, I disguised myself as a crew member of the Hayabusa Maru, stuffed this guy into a barrel, tied him to the submarine, and dragged him all the way here. The ship’s crew was so absorbed in their diving work that none of them noticed.” “Good, good. Well done. There’s nothing to worry about now… Hey, Kenkichi-kun, there’s no need to be so frightened. You’re an important hostage, you see. All you need to do is stay here and keep yourself occupied. If your father agrees to what I say, I’ll return you.”

The black monster spoke in a purring voice from the triangular cut-out mouth of his mask.

Kenkichi-kun mustered his courage and asked in return.

“What are you going to make Father do? What do I have to do for you to return me?”

Then, the black monster chuckled eerily. “Is that what you want to know? Quite a courageous lad, aren’t you? That’s simple—my demand is for you to hand over all of the Taiyōmaru’s gold ingots to me. If he agrees to my demand, then I’ll return you. Until then, you’re to stay right here without moving.”

Oh, Kenkichi-kun had been made into a terrifying hostage. Still, who on earth was this black monster? And what would become of Kenkichi-kun’s fate from here on out? And what terrifying things would those eight Iron Mermaids that had just left the cave begin to do?

Vanishing Fish-shaped Submarine

Aboard the *Hayabusa Maru*, preparations had finally been completed, and five divers descended to the seafloor to collect the scattered gold ingots. It was already around eight o'clock in the evening. The sea was pitch black.

They replaced the rope on the iron net and lowered it along with the divers. The five men carrying underwater lamps would find boxes of gold ingots on the seabed and carry them into the iron net. It took a full hour, but they finally managed to place eight boxes into the iron net. Initially, they had loaded fifteen boxes into the net, but seven had broken during the fall, scattering their golden contents that became buried in seabed sand and impossible to retrieve quickly. When eight boxes were secured in the net, one diver used his diving helmet telephone to request that the Hayabusa Maru hoist it up temporarily.

On the deck of the Hayabusa Maru, upon hearing that call, they hoisted up the iron net's rope vigorously using machinery. This time, no giant crab like before appeared, and the eight boxes safely reached the deck. The five divers remaining on the seabed next spread out and began searching for gold ingots buried in the sand. It wasn't just sand. The seabed teemed with dense growths of kelp-like seaweed, making the search for gold ingots sunken within them an excruciatingly laborious task.

However, the five men, intent on retrieving as many as possible, frantically roamed the pitch-black seabed.

Even if the underwater lamps were bright, they only illuminated three to four meters, making it feel like walking through an inkwell. Not even the figures of their fellow divers were visible at all. The faintly glowing underwater lamps were moving about here and there, but they couldn't discern any human figures.

When they suddenly noticed, two round lights were approaching from the distance at tremendous speed. They were not underwater lamps. They were much stronger lights. They closed in rapidly, right before their eyes. "Ah! It's the fish-shaped submarine!"

One of the divers cried out involuntarily. The voice reverberated through the receiver on the Hayabusa Maru's deck.

On the deck, an engineer was pressing the receiver to his ear when he heard that shout and immediately informed the captain. The captain ordered the radio operator to relay instructions to their submarine. This was to drive off the enemy’s fish-shaped submarine.

On the seabed, the fish-shaped submarine was approaching right in front of the divers. Because its two glaring eyes cast a hazy illumination across the area, the entire form of the fish-shaped submarine became dimly visible.

When the divers saw it, they were so overwhelmed with terror that their bodies went numb, leaving them unable to scream or flee. On the long back of the fish-shaped submarine, eerie-looking monsters were clustered together and clinging. Those were eight Iron Mermaids. Gathered there in a swarming mass were those terrifying monsters, all identical in form.

The fish-shaped submarine smoothly lowered its head and descended until it was skimming the seafloor. Then, the eight monsters that had been clustered on its back hopped down nimbly to the seabed. And then, taking on the appearance of giant crocodiles, they began crawling toward the divers!

“Pull us up! The Iron Mermaids are here! Hurry! Hurry!” The five divers screamed in unison. Their voices clanged through the Hayabusa Maru’s receiver.

The engineer hurriedly gave the hoisting signal to the machinery crew. With a clattering noise, the rope was wound up. Eventually, the five divers clambered up the ship's side in a frantic scramble. Once their diving helmets were removed, they proceeded to report in detail about the terrifying scene on the seabed.

Meanwhile, the allied submarine, having received a wireless order from the Hayabusa Maru, immediately rushed to the location where the divers were submerged.

By the time they arrived, the eight Iron Mermaids had just landed on the seabed. The enemy’s fish-shaped submarine had already detected the allied submarine and abruptly began to flee.

The two-eyed monstrous fish with glaring lights and the three-eyed submarine pursuing it—both raced across the seafloor at full speed. The fish of the seabed panicked at this sudden assault by enormous monsters and scattered in all directions. Illuminated by the two submarines' headlights, they flickered beautifully—glittering gold and silver.

The two submarines were separated by about fifty meters. The fleeing fish-shaped submarine was racing headlong toward the cape's shore, but just as it seemed about to reach the shore, its form abruptly vanished from sight.

Assuming it had turned off its two eye-like headlights, they used their own headlights to thoroughly scour the entire area. But that large fish-shaped submarine was nowhere to be seen—no shadow, no form. It had vanished without a trace, as if dissolved into the seawater. The seabed around there was all rugged rocks, some as large as small hills. For a long time, they circled around searching the shadows of those rocks, thinking the enemy might be hiding there, but there was no sign of them anywhere.

Such a large fish-shaped submarine couldn't possibly hide so effectively. They could only conclude it had vanished like a ghost.

Since there was no other choice, after informing the Hayabusa Maru via wireless of this development, the allied submarine decided to withdraw from the area.

Even so, what on earth had happened to the fish-shaped submarine? Such a large thing couldn't possibly have buried itself in the seabed's sand. The kelp forests weren't extensive enough to conceal the fish-shaped submarine either. Wondering if it might have surfaced, they too rose up to check, but there remained no trace of it. It was sorcery of the seabed. Had the Iron Mermaid's band of monsters mastered some strange sorcery?

Detective Akechi's Disguise

The wireless room of the Hayabusa Maru received word from their allied submarine that the fish-shaped submarine had vanished, but before they could process this shock, a strange wireless transmission soon came in from somewhere. After repeatedly calling out “Hayabusa Maru, Hayabusa Maru,” they began transmitting the same message over and over.

“We have Miyata Kenkichi-kun. Hand over all gold ingots from the Taiyomaru in exchange for his return.” “If you refuse to comply, consider Kenkichi-kun’s life forfeit—he will meet a tragic end.”

The wireless engineer rushed to the captain on deck with the hastily scribbled message. "What? They claim to have Kenkichi-kun?" "Mr. Miyata - where is Kenkichi right now?" "We've received this bizarre wireless transmission." Miyata-san and Detective Akechi took the paper from the captain's hand and read its terrifying contents.

“Kenkichi said he was going to his cabin and went down a while ago, but he hasn’t come back.”

Mr. Miyata turned deathly pale and muttered.

“Then let’s go check the cabin.”

Having said that, Akechi abruptly dashed toward the hatch that led down to the cabin. Mr. Miyata also started running after him. After a short while, Detective Akechi and Mr. Miyata came running back up to the deck.

“He’s not in the cabin.” “Everyone – the boy Kenkichi has disappeared.” “Please split up and search every part of the ship.”

Akechi shouted. Then chaos erupted as the crew members split into several groups and searched every corner of the ship, but there was no sign of the boy anywhere.

“It’s strange. Sailor Kitagawa is also missing. Could it be that guy…?” one of the sailors reported.

“That’s right! He might have been an enemy plant. There’s no way Kenkichi-kun would vanish from the ship on his own.”

The captain exclaimed in frustration.

“He might have been taken into the fish-shaped submarine.” “Because we were all focused on diving operations, even if their submarine surfaced on the opposite side and took Kenkichi-kun aboard, nobody would’ve noticed.”

When the engineer shared his theory, everyone else also thought that was probably the case. “However, if we don’t send a reply via wireless, Kenkichi might meet some terrible fate.” “But we can’t just hand over the gold ingots. Akechi-san, what should we do?” Miyata-san, his face pale, consulted Akechi. “We’ll send a wireless message asking them to wait for our reply until tomorrow.” “In the meantime, there’s something I want to try.” “With some luck, I might just be able to get Kenkichi-kun back safely.”

Akechi said with an air of confidence.

Thereupon, the captain summoned the engineer and had him send a wireless message requesting they wait for a reply until tomorrow. “Mr. Akechi, what exactly do you mean by this ‘something you want to try’?”

When the captain inquired, Akechi proposed something utterly unexpected.

“I think we should go ashore quietly tonight. If we use a boat, we risk alerting the enemy—it’s better to approach the coast in the submarine and swim the remaining distance to shore. I’ll take Kobayashi with me. I intend to return before tomorrow noon, though it may end up being later than that. Please keep delaying the wireless reply until I return.”

No matter how much everyone pressed him, Akechi refused to say anything more. However, both Mr. Miyata and the captain were well aware of the famous detective's skills, so without pressing him further, they consented to Akechi's landing.

Hearing this, the boy Kobayashi was overjoyed. The thought that he and the Detective would board the submarine and embark on an adventure together made him so excited he could hardly stand it.

Then, the two departed—already well past midnight. They lowered a boat from the Hayabusa Maru and transferred to the submarine floating nearby. The submarine immediately submerged, departed, and reached the coast in less than ten minutes. However, since that area was a desolate rocky shore with no pier, they couldn’t dock alongside. It surfaced at a point about a hundred meters away from the shore.

Detective Akechi and Kobayashi took off their clothes and shirts, rolled them up small along with their shoes, tied the bundle on top of their heads, and jumped into the water. That area was dominated by sheer cliffs of towering rock faces, beneath which fierce waves crashed against the base, churning the water into a foaming white frenzy. Amidst the sheer cliffs surrounding it, there was a single spot where the rocks sloped downward, and small fishing boats would dock there. The two began swimming vigorously toward the boat landing.

Of course Detective Akechi was a strong swimmer, and the boy Kobayashi was no slouch either. Together, they powered through the crashing waves, swimming vigorously until they clambered up onto the rocky shore. Then, after drying themselves off there and putting on their shirts and clothes, they climbed up the terraced rocks and hurried through the pitch-black wasteland toward the nearby fishing village. The area was a barren wasteland with neither rice paddies nor fields—just five or six fishermen’s houses clustered together in a truly desolate hamlet. Those five or six houses were all fast asleep, pitch-black and utterly silent.

The two roused the occupants of one house by knocking, offered a good sum of money to persuade the fishermen to part with some clothes, stripped off what they were wearing, and changed into them. In other words, they disguised themselves as a fisherman father and son. Their outfits consisted of grimy khaki trousers, a tattered shirt with patches, and hand towels tied around their heads as headbands. “Hmm, our faces are too pale. We should probably put on a bit of makeup.”

Akechi said this, gathered soot that had accumulated on the wall of the fisherman's house onto his hands, and thickly slathered it over his own face and Kobayashi's face. With this, the two completely transformed into convincing fishermen.

Then, sitting down there, they inquired in detail about the area's geography. After all, for this adventure, they needed to thoroughly familiarize themselves with the lay of the land.

As they continued talking like that, the eastern sky began to brighten dimly. It was the faint light before the sun rose.

Thereupon, the two thanked the fishermen and went outside. It was no longer so dark that they couldn’t see their footing, and no matter how far they walked, there was no danger. The two began walking along the coast, trudging steadily.

They didn’t walk straight ahead—if there was a pine grove, they searched through it; if there rose a towering hill, they scoured its perimeter; if there gaped a hole in the ground, they peered inside—wandering all the while as they hunted for something.

When they looked out to sea, the hull of the Hayabusa Maru was faintly visible as a dark shape. When the Hayabusa Maru came into its closest visible position, Detective Akechi was examining the area’s ground even more carefully than before when he suddenly stopped and stared at the pine grove ahead. There grew five or six large pine trees, and beneath them, low-growing trees were densely packed. The famous detective discovered something within that thicket.

“Be quiet. Don’t make a sound.” After whispering this to Kobayashi and approaching the spot, he hid himself in the shadow of a thick pine trunk and peered through the dense thicket beyond. Though still dim in the predawn darkness, their eyes gradually adjusted as they kept watching until the surroundings came into clear view.

“Oh? Could there be a mole in a place like this?”

The boy Kobayashi stared at the spot in surprise. The grass in the thicket shook violently. Detective Akechi, keen as a hunting dog, must have noticed it earlier.

The grass began shaking with increasing violence. A patch of ground about sixty centimeters square, along with the grass, began rising up with a groan. And in an instant, the grassy ground shifted sideways, leaving behind a pitch-black square hole.

And then, something truly mysterious occurred. From that square hole, something slid out its head! It was not a mole's head, but a human one. The man attached to that head cautiously glanced around his surroundings, but having noticed neither of the two observers and presumably thinking no one was there, he emerged fully from the hole. Indeed, he looked every bit like a local fisherman. He was a robust-looking man of about thirty-five or thirty-six.

What in the world was going on here? A human being had emerged from within the coastal ground. Did this man live in the soil like a ground spider? What could lie beneath that black hole? Had that space been widened like an air-raid shelter to serve as a human dwelling?

The suspicious man who had emerged from the hole restored the grassy soil to its original place and sealed the hole shut. Then, after scanning his surroundings thoroughly once more, he set off at a brisk pace toward his destination.

Detective Akechi, upon seeing this, poked the boy Kobayashi's arm and signaled. And then, so as not to be noticed by their target, they stealthily began tailing the man.

The suspicious man walked briskly along the coast in the opposite direction. In that direction, unlike the hamlet from before, there was a much larger fishing village.

On that path loomed a tall hill. The man trudged steadily along the hill's base. At that moment, Detective Akechi jabbed Kobayashi's arm again. Then they suddenly broke into a sprint. The speed was terrifying. It resembled a dark wind whipping past. Kobayashi too followed, running with desperate intensity. Akechi's shadowy figure lunged at the suspicious man from behind. And in an instant, pinned him to the ground.

The Naked Warrior Why had Detective Akechi captured that man? And where had he taken him, and what had he done?

The narrative left that aside for now and shifted to events that occurred around noon that day, five or six hours later.

Aboard the Hayabusa Maru anchored offshore, Mr. Miyata, the captain, the salvage company engineer, and many other crew members had come up to the deck and were gazing intently at the sea surface.

A small boat was approaching the Hayabusa Maru from the shore. On board were an adult, a child, and two fishermen. The adult was the one rowing.

Before long, the small boat came right beneath the Hayabusa Maru. Then, waving his hand toward the people on deck, he shouted loudly.

“Lower the ladder.”

A fisherman they didn’t recognize was requesting passage aboard the Hayabusa Maru. “Who are you…?” “What business do you have…?”

From the deck，someone called out loudly． “I am Akechi．” “Take a good look at my face．” “And this here is Kobayashi…”

The people on deck were astonished upon hearing Detective Akechi. However, upon closer inspection—though his face was smeared with black grime—they saw it was unmistakably Akechi and hurried to lower the ladder. Akechi in fisherman attire and the boy Kobayashi climbed the ladder up to the deck and entered the lower cabin with Mr. Miyata, the captain, the engineer, and others. After about thirty minutes of discussion, Detective Akechi emerged onto the deck carrying a large black cloth-wrapped bundle under his arm. Then he and Kobayashi climbed back into their original small boat and headed straight for the rocky coast.

After the two departed, the interior of the Hayabusa Maru suddenly grew hectic. The captain gathered the crew members and sailors and issued a certain command. Then, the crew members and sailors began bustling about here and there, starting some sort of preparation. It was a commotion as if war were about to break out. The radio operator called back their submarine via wireless, and soon, that small submarine surfaced right beside the Hayabusa Maru. Then, a boat from the Hayabusa Maru was lowered, and thirteen naked crew members and sailors boarded it. They were completely naked except for their underpants. They all had shoulders with muscles bulging impressively, and their arms bore large, powerful-looking bulges—every one of them appeared strong.

All those naked men had oxygen tanks strapped to their backs, held diving goggles, wore large flippers on their feet, and carried oddly shaped underwater rifles in their hands. The boat was tied behind the submarine with a rope, and before long, the submarine, remaining on the surface of the sea, began towing the boat toward some destination.

About twenty minutes later, the submarine sank to the rocky seabed near the cape, its three headlights glaring brightly. On the other side of that cliff-like rock lay a large hollow cave. This was precisely where the enemy's fish-shaped submarine had vanished without warning the previous night. At that time, the cave had remained hidden behind a towering rocky massif that loomed before its entrance.

Earlier, Detective Akechi had left instructions that there must be a cave near where the enemy's fish-shaped submarine had disappeared, so their submarine had searched around and finally found it. The cave was just large enough for the fish-shaped submarine to squeeze in. The back was pitch black and impossible to see, but it appeared to be an extremely deep cavern. The thirteen naked warriors, who had ridden in the boat towed by their submarine, dove from the boat into the seabed and were now swimming around the entrance to the cavern.

Last night, the Iron Mermaids that had appeared along the coast near the Hayabusa Maru must have gathered up the gold ingots scattered around there and returned to this very cave. Those Iron Mermaid fiends might emerge again at any moment. If they emerged, the naked warriors lay in wait, ready to shoot them with underwater rifles. The sight of thirteen naked warriors wearing underwater goggles, carrying oxygen tanks on their backs, large flippers on their feet, and wielding underwater rifles as they swam vigorously in every direction around the cavern entrance was truly an awe-inspiring spectacle. Some were diving into the cavern, trying to investigate the interior.

Thanks to Detective Akechi's report confirming that Kenkichi had also been taken into this cavern, they were attempting to swim deep into its recesses to find him, seizing this chance.

Even so, what kind of terrible ordeal was Kenkichi-kun suffering at the hands of the monster gang inside the cavern?

The Cavern Dungeon

At that moment, Kenkichi-kun was confined within the cavern dungeon. The cavern where the naked warriors were swimming around widened as one progressed deeper, and there the enemy’s fish-shaped submarine lay hidden; proceeding even further, the passage gradually sloped upward until it rose above sea level, becoming a dry cavern. And there were intricate escape routes resembling those in a solutional cave, with room-like spacious areas scattered here and there. The Iron Mermaid monster gang had discovered this unknown cave and made it their stronghold.

In one of the winding branch paths, there was a depression resembling a room about two tatami mats in size, and before it stood something like the frame of a prison cell constructed by crisscrossing cedar logs. It was a dungeon inside the cave.

In the pitch-black dungeon, a boy in a school uniform sat huddled dejectedly. That was Kenkichi. They brought him food properly and didn't particularly mistreat him, but confined within the cage as he was, he couldn't go anywhere. With no one to talk to and nothing visible in the pitch-black darkness, he had no choice but to remain still. It was a truly lonely and desolate existence.

"I wonder what Mr. Kobayashi and Detective Akechi are doing now." "No one could possibly know I was brought here." "Even Detective Akechi wouldn't notice." "Ah... I want to see Dad..." "Why did I have to board that Hayabusa Maru?" "I shouldn't have done it." "If only I hadn't, I'd be home in Tokyo with Mom right now." As these thoughts flooded him, Kenkichi suddenly wanted to shout, "Dad... Mom..." at the top of his lungs. Hot tears spilled from both eyes, rolling down his cheeks in steady streams.

When he suddenly noticed, a flickering light was shining on the rocky wall outside the cage. It seemed someone was shining a flashlight and coming this way. "Could one of the bandit’s underlings be bringing food?" he wondered, but it was still too early for that.

"Could it be that they’re going to take me out of this cage and subject me to something terrible?" Suddenly, as that thought crossed his mind, Kenkichi-kun became so terrified he could hardly stand it. Before he knew it, he shrank into a corner of the cave and trembled uncontrollably. The light reflecting off the uneven rock walls gradually grew stronger, and soon, a flashlight swaying like a monster’s eyeball approached from the other side.

When he saw that, Kenkichi-kun’s heart began pounding at a terrifying speed, as if someone were beating a drum. The flashlight came to a complete stop right in front of the bars of the prison cell where Kenkichi-kun was confined. And then, after slowly sweeping the flashlight beam across the rocky dungeon, the man who had come there directed the light toward his own face. He was one of the bandit’s subordinates who always brought him food.

The man held a flashlight in his right hand and carried a large black cloth-wrapped bundle, roughly the size of a child's body, in his left. It was an unidentifiable thing of ominously grotesque shape. As Kenkichi-kun wondered what on earth could be inside that black cloth-wrapped bundle, he became even more terrified, his body beginning to tremble uncontrollably.

“Kenkichi-kun…”

The man called out. It was a gentle voice. Kenkichi-kun thought, "Huh? That’s strange." Because it was completely different from the man’s usual voice. “It’s me—it’s me! I may be disguised as one of those villains, but look closely—I’m Akechi.”

Hearing this, Kenkichi-kun gasped and involuntarily stood up. Drawing near the bars, he stared at the man's face. Though disguised exactly like one of the gang members, upon closer inspection it was Detective Akechi. From within the face darkened with makeup, the detective's familiar features seemed to emerge smoothly, appearing to float into view.

“Ah, Detective!”

Kenkichi-kun clung to the bars and cried out involuntarily.

“You mustn’t make such a loud noise. I’ve come to rescue you. Kobayashi will be here soon, you see.” Detective Akechi said this, raised his flashlight high, and swung it two or three times to illuminate the tunnel-like hollow cave ahead.

Then, as if that had been a signal, someone approached from the pitch-black distance ahead. When they entered the beam of Akechi’s flashlight, it was a boy dressed in fisherman-like clothing. Huh? A strange child has come, he thought. Upon closer inspection, though the boy’s face had been blackened with soot, there was something reminiscent of Kobayashi about him. It was indeed Kobayashi in disguise.

“Ah, Mr. Kobayashi…” Kenkichi could not help but cry out again.

Detective Akechi took out the key he had prepared, opened the door of the prison cell bars, and entered inside with Kobayashi. "Kenkichi-kun, I'm glad you're safe." Kobayashi suddenly hugged Kenkichi-kun tightly. Kenkichi-kun also clung to Kobayashi, and like long-lost brothers reunited, they remained locked in an embrace, unwilling to part. "Kenkichi-kun, rescuing you will require all sorts of tricks—it's quite a difficult job." "Moreover, if we dawdle and get spotted by the enemy, it'll be disastrous—we must work swiftly." "I'll explain details later—let's begin the trick immediately." "First, you must exchange clothes with Kobayashi-kun."

Detective Akechi said this and, lending a hand himself, swiftly helped the two exchange clothes. In other words, Kobayashi-kun donned the school uniform to impersonate Kenkichi-kun, while Kenkichi-kun put on the fisherman's-child clothing Kobayashi-kun had been wearing. Once they changed clothes, Akechi took a damp hand towel from his pocket and thoroughly wiped the soot from Kobayashi-kun's face. Then using the now-dirtied towel, he rubbed it all over Kenkichi-kun's face. This left Kobayashi-kun's previously grimy face clean, while Kenkichi-kun—who had been clean—transformed in an instant into a sunburned fisherman's child.

“You’ll escape with me through the hole leading to land and return by boarding the Hayabusa Maru. “I’ll take off these clothes and put on a fisherman’s outfit too. That way, everyone will think a fisherman and his child are on the boat, and no one will suspect a thing.” With those words, Akechi handed the large cloth-wrapped bundle he had been carrying under his left arm earlier to Kobayashi boy, now impersonating Kenkichi-kun.

“Listen carefully. This should do the trick. I’ll be back soon. Until then, use your skills to keep the enemies under control.” “Yes, everything’s under control. I’ll definitely handle it well.”

Kobayashi-kun answered energetically. Then Detective Akechi stepped outside the bars, changed into the fisherman's clothes he had hidden in a nearby rock crevice, and hurried toward the small hole leading to land—taking Kenkichi with him as they wound through the rocky tunnels.

After some time had passed, something inexplicably bizarre occurred within the thieves' cave. As one of the gang members walked through the rocky tunnel holding a flashlight, he glimpsed something like a black human shadow flickering in motion ahead. Somehow it appeared to be an extremely short figure resembling a child. The thug's subordinate halted abruptly with a start.

“There’s no way that little runt is one of us.” “Could Kenkichi have broken out of the cell and escaped?” If that were true, it’d spell trouble. The man snapped into action, lunging after the shadowy figure. “Hey! Who’s there?” “Stop! Don’t even think about running!” He swung his flashlight wildly as he charged forward, but the diminutive shadow darted through the labyrinthine cavern with squirrel-like nimbleness, weaving through the twisting passages until it vanished from sight.

"Tch! That slippery brat," he spat into the darkness. If this shadow truly were Kenkichi... then iron bars would guard nothing but air within his cell. "Right - time to verify."

The man, thinking this, hurried toward the prison cell. And then, when he stood outside the cell bars and shone his flashlight inside to look—strangely enough—the boy Kenkichi was indeed right there. In the far corner of the rocky cell, he crouched motionless with his head hung low. The man thought to go inside and investigate, but the cell door had a large padlock that couldn’t be opened without a key. The key was held by that thug’s subordinate wearing the jumper—the one Detective Akechi was disguised as. So, the man began running toward the wide cave where everyone was gathered to search for that subordinate.

As he ran through the rocky tunnel, once again a small black figure flickered into view in the darkness ahead. He hurriedly swung his flashlight toward it. The figure abruptly ducked around the bend, but not before he saw it wore a school uniform identical to Kenkichi-kun's. The height matched perfectly too. The man felt a strange sensation, as if caught in a dream. There were now two Kenkichi-kuns. One crouched inside the locked prison cell. The other dashed freely through the cave. Nothing could be more bizarre. An uneasy feeling crept over him. Without hesitation, he rushed into the black-masked leader's chamber and reported everything. The leader immediately ordered everyone to search for Jack—the one holding the cell key.

However, even after the thieves' underlings divided up and searched throughout the cave for nearly thirty minutes, they simply could not find either the mysterious child or Jack.

It was around the time another thirty minutes had passed since that search had ended in vain. One of the subordinates rushed into the leader’s room and frantically reported.

“Boss! He’s here, he’s here! Jack, the guy in charge of Kenkichi, suddenly showed up out of nowhere. He’s coming here now.”

Jack was the nickname of the man who held the key to the prison cell's bars. Before the report could even finish, Jack slid into view at the entrance to the leader's room. That man in the jumper and khaki pants.

The Mysterious Boy The leader summoned Jack before the table and rebuked him. “Jack, where have you been? “We’ve been searching for you for nearly an hour. “Where in the world have you been fooling around all this time?”

Jack, who stood before the leader, grinned and scratched his head.

“I went to the village and was treated to a meal at a fisherman’s house, so I ended up being late…” “What?! You went to the village to fool around? I told you explicitly—finish your business and return immediately! What if fishermen you associate with discover this hideout?”

“Oh‚ my apologies. “I’ll be more careful from now on.”

Jack bowed his head earnestly. “You’re holding the prison cell key. Something strange has happened in that cell. It seems Kenkichi has escaped. He keeps darting about in the cave. But when did that kid become so quick? No matter how hard they chase him, they just can’t catch him.”

However, when they went to the prison cell and peered through the bars, Kenkichi was right there crouching inside. It made no sense at all. Everyone kept saying there were two Kenkichis now. But that was impossible. "One of them has to be a fake," said the Black Hooded Leader. "We tried to check on Kenkichi in the prison cell, but there's no key to open it. You're the one who has the key. Let's go inspect that cell right now. You haven't lost it... have you?"

“Oh. “I have it right here with me.” “Then I’ll accompany you to the prison cell.” Jack said this and took the lead. The black-masked leader in a cloak followed behind him.

The two passed through the pitch-dark rock tunnel and arrived before the prison cell. Jack unlocked the prison cell door with the key, and the two stepped inside.

When they looked, Kenkichi was crouching in the corner of the rocky cell, head bowed. Even as the two entered, he didn’t move a muscle. He remained so still that one might wonder whether he was asleep or perhaps even dead. The leader strode briskly to his side, grabbed the head of Kenkichi—crouching with bowed head—and forcefully tilted his face upward, but upon seeing that face—

“Ah!”

He let out a cry and staggered backward unsteadily. Because that was not a human face. Jack was also startled upon seeing it.

Why were the two so startled? Because what they saw wasn't a living human face - it was a mannequin's face. Because this was the face of a child mannequin arranged in a clothing store's display window.

When the leader realized it was a doll, he yanked off its jacket in frustration as if tearing it away, only to discover the body was been made of a bundle of straw. They had dressed a straw bundle in clothes to make it look like Kenkichi. “That Kenkichi brat deceived us with this doll and still escaped after all.” “Damn you!” Suddenly, he yanked out the straw bundle and stomped on it. In that instant, the doll’s head came off and rolled away clattering, looking exactly as though a boy had been beheaded.

Even so, who on earth had brought the doll’s head and straw bundle? Moreover, what on earth was Kenkichi, the boy who had dressed the doll in clothes and escaped, wearing?

The leader tilted his head with a look of utter bewilderment. However, dear readers, you are already well aware of this. Detective Akechi—disguised as Jack, a member of the gang—had brought the doll’s head and straw bundle from the Hayabusa Maru into the prison cell, dressed them in Kenkichi’s clothes, put Kenkichi in the fisherman’s garments Kobayashi had been wearing, donned fisherman’s attire himself, and taken the real Kenkichi back by ship to the Hayabusa Maru.

Therefore, the child darting in and out of sight within the cave was not Kenkichi but Kobayashi. Kobayashi was wearing Kenkichi’s clothes and was in disguise. However, the gang leader knew nothing. Because the cave was dark and Akechi’s disguise was skillfully crafted, the leader remained convinced that he was the real Jack.

“Alright, I’ll catch Kenkichi myself. “He must still be in the cave. “Jack, you help too!”

The leader exited the prison cell and began pacing around inside the pitch-dark rock tunnel. Jack shone a flashlight from behind and followed along.

After walking for some time, they saw a small black shadow dart across ahead. “Ah! There he is!” “That must be Kenkichi.” “I won’t let you escape this time!” The masked leader fluttered his black cloak and broke into a run toward it. Jack followed close behind. “There he is! There he is!” “He’s running over there.” “That’s definitely Kenkichi, that brat!” The leader quickened his pace further. A child couldn’t outrun an adult. The gap between pursuer and pursued visibly closed. Oh no—was Kobayashi, disguised as Kenkichi, about to be caught any moment now?

“Ah! He’s climbing the stairs! Trying to escape outside the cave!” The leader spat irritably as he ran. Atop those stone stairs lay a small hole opening onto the land above.

The leader rushed to the stairs as if flying and tried to grab the boy’s clothes from below. He was just about thirty centimeters away—his hand nearly within reach.

However, the boy was quicker. He pushed aside the hard clump of earth overgrown with grass at the exit leading above ground and burst out through the hole. The masked leader stuck his face out of the hole immediately after, but upon catching a glimpse of what was there, he gasped and jerked his head back in.

Because there was something terrifying outside the hole. Five or six uniformed police officers stood lined up in the forest beyond the hole—how and when they had arrived was unclear—glaring in their direction. Kobayashi, disguised as Kenkichi, stood smiling amidst the officers. "This is bad! The police are here! Jack, run! Hurry up and run!"

The leader hurriedly descended the stone stairs and began running deeper into the cave while pushing Jack ahead. The two desperately raced through the winding tunnel. The place they reached was a vast cavern near the sea. There dwelled those eight terrifying Iron Mermaids, swarming in a writhing mass.

The Secret of the Monsters

In the spacious cave, eight Iron Mermaids were clustered together like beasts in a cage. On their iron-forged, terrifying faces were large eyes glowing a phosphorescent blue, mouths split open to the ears, and fangs jutting out sharply from between those lips. Their entire bodies were covered in iron scales, and sharp, crest-like serrations of iron ran from their heads down to their backs. Their torsos and tails were exactly like an alligator’s, and just like the rest, were made of iron. They were larger than adult humans.

Even one of them was terrifying enough, but with eight such monsters swarming together in a clustered mass, the eeriness was beyond imagination. Guided by the light of Jack’s flashlight, the masked leader entered the monsters’ den. Then, facing the Iron Mermaids, he commanded in a loud voice: “Listen carefully, all of you. The police are about to storm in from the land entrance. You lot will go halfway and attack them. Drive every last one of them out of the hole! Then fill it from inside with huge stones so they can’t get back in again! Understood? Now, everyone—let’s head out together!”

The iron monsters listened to their leader’s command in silence. Then, after what seemed like a period of complete stillness, a dreadful metallic cacophony erupted—as if countless iron plates were grating against each other in unison: "Clang! Clang! Clang! Clang! Clang!" The Iron Mermaids were laughing together in perfect sync. “Hey! What’s gotten into you all?” “Do you not recognize me?” “Why are you laughing?” “Why won’t you obey my orders?!”

The leader roared in a terrifying voice. However, the clashing iron sounds showed no sign of subsiding; instead, they grew increasingly violent. The monsters kept mocking the leader, laughing endlessly. "You've all gone mad!" "Fine! I'll make you regret this!"

The leader suddenly raised his foot and kicked one of the nearby mermaids in the face.

Then suddenly, with a dreadful shift in rhythm from the "Clang, clang, clang, clang" sounds, eight Iron Mermaids lunged at the leader from all directions. The phosphorescent light in their eyes flared up intensely; they gnashed their sharp fangs with a clatter, spread both hands tipped with razor-sharp claws, surrounded the leader, and revealed a terrifying visage poised to strike at any moment.

Even the leader of the monster gang froze in terror upon seeing this. He had no idea why this was happening. What on earth could have caused his subordinate mermaids to suddenly rebel against their leader? Then, at that moment, yet another strange thing occurred.

The monsters' laughter—"Clang, clang, clang, clang, clang..."—suddenly transformed into a human voice: "Bwahahaha..." The eight mermaids began to laugh like humans. It was a terrifying laughter that made the very cave tremble. Then, no sooner had a loud clattering noise erupted than the mermaids' bellies split open, and naked humans came leaping out from inside them.

“Bwahahaha… How about that? Surprised?” “We’re not your subordinates.” “We’re the eight brave warriors from the Hayabusa Maru.” The first young man to leap out from among the Iron Mermaids barked. Indeed, they were not subordinates. All eight of them were complete strangers. When he saw this, the Black Hooded Leader froze in place, his power of speech completely gone.

“Bwahahaha… You’re surprised. “Iron Mermaids are nothing but toys. “They’re made by shaping iron plates like this, with three oxygen tanks attached inside. “So even if they stay underwater for a long time, they’re just fine. “Your subordinates got inside them and were scaring us. “The reason their eyes glow phosphorescently is because there are small blue bulbs powered by dry batteries inside.”

Detective Akechi had seen right through it all. "And then he sent us naked warriors down to the seabed. We strapped on oxygen tanks and sneaked in through the cave entrance at the ocean floor. With underwater guns, we scared your eight lackeys into stripping off those mermaid iron shells so we could take their place. Your eight goons are trussed up with ropes, gagged with monkey muzzles, and tossed into a rock hole over there. Bwahahaha... What do you think of that? Surprised?"

The masked leader had never once suffered such humiliation before. It was a terrible defeat. However, this was no time to dawdle. The eight naked warriors looked ready to leap at them at any moment. “Jack, follow me.” The leader roared this, then whirled around and darted off like an arrow. However, where on earth did he intend to flee to this time?

He fluttered his black cloak and ran toward the exit leading to the bottom of the sea. Jack followed right behind him.

After running for a while, suddenly, the space before them opened up. There, water that had entered from the seabed had formed into a pool. It was a pool in a spacious cave. The entrance from the seabed lay far below the water surface, but because the cave continued diagonally upward, that area now sat above the water level, with seawater pooled at the cave floor like a pond.

At the edge of the pool floated a pitch-black object about the size of a small whale. It was the enemy's fish-shaped submarine. On its back was a transparent, lump-like protuberance. This was a viewing window made of plastic glass. Moreover, it had been designed to open upward on hinges and also served as the submarine's entrance and exit. The Black Hooded Leader ran toward the shore, leading Jack with him.

“Now, get on this. And then we make our escape to the bottom of the sea.”

Saying this, he took the long plank placed at the water's edge, laid it across the back of the fish-shaped submarine, walked over it to the glass viewing window, opened it, and abruptly slid inside the vessel.

“Jack, you get in too. And then you’ll operate this.”

Summoned by the Black Hooded Leader, Jack also crossed the plank and slid into the submarine. And then—after firmly closing the viewing window and taking his seat at the controls—he let out a piercing cry. "Oh no, Boss! This is bad!" "The machinery’s completely wrecked!" "Huh? The machinery?" The leader also rushed over and inspected the machinery, but it appeared someone had smashed it with a hammer, making immediate repairs utterly impossible.

“It can’t be helped. It’s the final escape route.” The leader ground his teeth and barked. “Huh? The final escape route?”

“Beyond this lies a branch path in the cave that only I know. We’ll take refuge there.”

The two hurriedly opened the viewing window and returned to the original rocky shore.

When they looked behind them in the cave, the eight naked warriors and police officers were shining flashlights and hurrying toward them.

“Come on! Hurry—this way!”

The leader called out to Jack and started running. When they turned a corner, they came to a stop in a hollow of the rock. Placing their hands on a crevice there, they pulled with all their might and shifted a boulder roughly sixty centimeters wide. Behind it lay a hole just large enough for a person to squeeze through. “Hurry—get in here. Make sure to put the rock back exactly as it was. If we do that, no one will notice. That way we’ll be safe.”

The two of them struggled into the hole, painstakingly returned the rock to its original place, and sealed it shut.

The Giant and the Phantom "This hole runs deep with many branching paths. "We're safe now. "There's absolutely no chance of being discovered."

The Black Hooded Leader said with confidence as he walked deeper into the rocky passage. "But this is strange," he said. "Police are coming in from the land exit, enemy guys are inside the Iron Mermaids, and somehow someone's wrecked all our submarine machinery—what on earth could've happened?"

From behind while following the Black Hooded Leader, Jack called out. "Hmm, all of this must be Akechi Kogorou's doing. "That guy must have found this cave somehow. "And he must have plotted all sorts of things. "Still, what I can't figure out is that Kenkichi brat. "How on earth did that quiet child become so nimble all of a sudden? It's truly baffling."

As the cave ceiling dropped significantly lower, the Black Hooded Leader walked hunched over and spoke to Jack behind him. Then Jack, finding something amusing, chuckled quietly and— “You still don’t understand why, do you?”

he said something strange.

Hearing this voice, the Black Hooded Leader stopped in surprise and turned toward where Jack’s voice had come from.

“What did you say? So you do understand?” “I know, of course. That child isn’t Kenkichi.” “What? Not Kenkichi? Then who the hell is that? And where has Kenkichi gone?”

“Kenkichi has returned to the Hayabusa Maru offshore.” “Why did he return? Surely he didn’t swim there?” “He went by a small boat.” “Where was that small boat?” “And who rowed it?” “Akechi Kogorou rowed it.” “The boat was borrowed from fishermen.” “Akechi and Kenkichi disguised themselves as father-and-son fishermen and deceived our eyes.”

Hearing this, the Black Hooded Leader tightly grabbed Jack’s arm in the darkness.

“You knew this all along—why did you stay silent until now? Why didn’t you inform me?” “There’s a reason for this. I’ll explain later. More importantly, it’s really cramped here. Let’s move to a wider space.” “Right—if we go further back, it’ll open up again. Come this way.”

The Black Hooded Leader said this and took the lead, proceeding forward while bending his body. After walking about ten meters, they emerged into a spacious cave. “Now then, this should do. If Kenkichi escaped to the Hayabusa Maru, then who the hell was that kid I chased earlier?” “That was Kobayashi, Detective Akechi Kogorou’s boy assistant.” “What?! That was Kobayashi?!” “That’s right. Kenkichi couldn’t possibly move around that nimbly, you see. In other words, this is how it happened. Akechi Kogorou sneaked into the cave with Kobayashi, carrying a mannequin’s head and a straw bundle. They dressed the straw bundle in Kenkichi’s clothes, attached the mannequin’s head, and sat it in the corner of the prison cell; they dressed Kenkichi in a fisherman’s child’s outfit and took him back to the Hayabusa Maru. After that, Kobayashi ran around inside the cave to create the illusion that there were two Kenkichis.”

“But wait— “How on earth did Akechi open the prison cell door? “Seeing that it isn’t broken, I can only assume it was opened with a key... “No one else should have that key besides you. “You didn’t lend the key to Akechi, did you?” “That’s right. I don’t recall lending it.” “Then how did Akechi open the prison cell door?” “Leader, it’s a riddle. “It’s quite an interesting riddle—can’t you solve it?”

At these mocking words, the leader began to get angry. "Hey, Jack! Are you trying to mess with me?" "This isn't the time for your riddle games!" "You're still hiding something from me."

Jack continued speaking calmly. “In other words, here’s the riddle." "There is only one key." "That key was held by this Jack." However, the one who opened the prison cell door was Akechi Kogorou. “Now then, what could be the answer to this riddle?”

In the darkness, the leader remained silent. He was so startled that he couldn't speak. Before long, the leader's trembling voice could be heard. "Then... you're...!" "Hahaha... Seems you've figured it out." "The answer is that Jack and Akechi were the same person." "Since we're one and the same, I never needed to borrow the key."

The cave was suddenly illuminated. Jack turned on his flashlight and shone it on his own face. In that circular beam of light, instead of Jack's features, there was Detective Akechi Kogorou's face with its trademark unruly mop of hair, grinning broadly.

In the darkness, he had removed the wig, peeled off the false eyebrows, wiped away the makeup from his face, and returned to his original self as Akechi. “So you really were Akechi after all!”

The beam of the flashlight was directed toward the leader. The black-masked fiend stood in a terrifying pose, arms spread wide, poised to lunge at Akechi.

“You’ve finally figured it out, haven’t you? For someone like you, it took quite a while to notice, didn’t it? But there's still a mystery remaining. Then where did the real Jack go? When did Jack and I switch places? You’re dying to know that, aren’t you?”

“I thought there must surely be an escape route to land within this cave. So I disguised myself as a local fisherman and was searching along the coastal cliff when Jack came crawling out from that hole in the woods. I followed Jack’s trail, then suddenly attacked him from behind and tied him up. And then I took him to the police in that village over there. From that moment onward, I had already coordinated everything with the police.”

“I returned once to the Hayabusa Maru and made thirteen naked warriors sneak through the undersea cave’s entrance. It was those brave warriors who defeated your subordinates inside the Iron Mermaids.” “Then I disguised myself as Jack, brought Kobayashi along, entered the cave from land, rescued Kenkichi, put him on a boat, and delivered him to the Hayabusa Maru. Then I came back here again.” “That’s why Jack vanished from sight for some time.”

“Hahahaha! How unfortunate—the Iron Mermaid fiend gang has been completely annihilated now!”

The circular beam of the flashlight had been continuously illuminating the masked leader since earlier. He remained completely still and silent, as if he had turned into a black stone.

Akechi still continued speaking. "You invented the Iron Mermaid to astonish the world. You attached oxygen tanks to thin iron armor so that a person inside could remain unharmed even at the bottom of the water."

Because such a terrifying contraption had come looming up from the sea, those who saw it thought it was a real monster. Even the newspapers made a big deal out of it.

You somehow tried to uncover the secret of the Taiyō Maru’s gold ingots and steal the captain’s will but failed. And then Kenkichi’s father Mr. Miyata became responsible for salvaging the gold ingots, and the Hayabusa Maru arrived at this offshore location.

"When you learned that, you established your stronghold in this cave and attempted to steal the gold ingots. Thus began the underwater battle. Afterward, all manner of strange phenomena occurred. Since we remained unaware of this cave's secrets, everything struck us as profoundly mysterious."

“But finally, I found this cave. And then, disguised as Jack, I entered here—and when I investigated, I completely uncovered your schemes and the secrets of the Iron Mermaid.” “And that’s how I won. Now then—shall I finally have you remove that mask? Though I can’t say for certain whether there’s even a real face beneath it.” No sooner had he spoken than Akechi lunged at the leader and tore off the black velvet mask as if ripping it away.

“Twenty Faces!” “It was you after all.” In the beam of the flashlight appeared one of the familiar faces of the fiend Twenty Faces—or perhaps Forty Faces. It remained unclear whether this was his true face, but it matched one they had seen during a previous case.

When told this, Twenty Faces looked momentarily startled, but quickly regained his composure and laughed defiantly.

“Heh heh heh… Detective Akechi, it’s been a while, hasn’t it? So what do you plan to do now?” “Isn’t it obvious? I’m turning you over to the police.” “Heh heh heh… You’re quite confident, aren’t you? Do you actually think I’d let myself get caught by you?” “This is how!” Just as Akechi lunged to grapple Twenty Faces, the opponent slipped beneath his hands and suddenly fled toward the back of the cave.

The End of the Monster Crab Akechi swung his flashlight to illuminate the path and pursued him. But Twenty Faces moved with incredible speed - he rounded the rocky corner ahead and disappeared from view. When Akechi reached that rock corner, the cave passage split into two paths. There was no telling which way Twenty Faces had fled. Akechi hesitated there briefly, allowing the gap between them to widen further.

Since there was no other choice, he proceeded while illuminating one of the rock holes with his flashlight, but after going about twenty meters, it became a dead end. In great haste, he turned back and returned to the original fork in the path. And he entered the other rock hole. After proceeding for a while, there was something hazy squirming in the distance. It was an enormous, ominous thing. Akechi directed the flashlight’s beam toward it. Then, the murky shape came into clear view.

That was a giant crab, twice the size of a human. It glared in their direction with bulging eyes, brandished massive claws, and scuttled away on eight sinister legs with a rustling sound. It was the monster crab. Though Akechi hadn't seen it himself before, this was that very monster crab which had once severed the Hayabusa Maru's gold ingot salvage rope. There was no way such a gigantic crab could actually exist. It was a crab made of iron plates. And Twenty Faces must have been hiding inside it.

When Akechi approached it, the monster crab quickly fled. When he stopped moving forward, the crab halted too, swiveling its bulging eyes and brandishing massive claws in a posture that seemed to say, "Stay back!" Since the monster crab scuttled sideways on eight legs, its escape was remarkably swift, and even the great Akechi found it difficult to catch up.

The cave became an upward slope that gradually grew steeper. Akechi kept pursuing the Monster Crab without respite. When he lunged at it, the crab rustled away in retreat. Its speed made capture utterly impossible.

Suddenly, he noticed the area ahead had begun to brighten faintly. "Oh?" he thought. "This is strange." When he looked closely, he realized this cave had an exit where outside light streamed through. Since they had climbed such a steep slope, that exit must have been situated at a considerable height.

The Monster Crab charged toward the exit with terrifying speed. There, just like a tunnel exit, a round hole had opened, its brightness nearly blinding. No sooner had the ugly form of the Monster Crab loomed as a pitch-black shadow blocking the exit than it swiftly vanished outside the hole.

Startled, Akechi dashed to the hole and peered outside, but the moment he looked, a wave of dizziness struck him, and he instinctively jerked his head back.

The exit was opened at the very top of a towering cliff. Sheer cliff-like rocks continued far below, where there was a foaming sea. It was several tens of meters above the sea. When he cautiously peered out, the Monster Crab clung to the sheer cliff face with its eight legs, descending lower and lower. Because it wasn't a real crab, it couldn't grip the rocks nearly as effectively. It looked ready to slip off at any moment—just watching it made one's backside tingle with unease.

“Ah!”

Akechi involuntarily cried out. The Monster Crab slipped with a grinding scrape. Once it started slipping, there was no stopping it. The eight legs lost their grip on the rocks, and the giant crab swooshed downward. Rapidly shrinking, it vanished into the churning sea. Even having fallen into the sea, Twenty Faces inside the Monster Crab likely hadn't died. That crab had once walked calmly along the seafloor. There must have been oxygen tanks installed inside it too - Twenty Faces was probably using them to breathe while crawling across the seabed.

He might escape somewhere like that after all. However, the cautious Detective Akechi had thoroughly taken even such a case into account.

When he had moved the rock at the entrance and entered this cave earlier, he had hurriedly torn a page from his notebook, written something with a pencil, and dropped it through a crevice in the rock to the outside. The eight brave warriors who had been pursuing the leader and Kobayashi must have found it. And following the instructions written there, the eight naked warriors—equipped with diving masks, oxygen tanks, and flippers—would have swum out of the subsea cave to join five warriors waiting there, lying in wait for the enemy to appear on the seabed.

That proceeded exactly as Akechi had planned. The thirteen naked warriors were swimming vigorously around the cave entrance.

Then, from above the sea, a large object came plummeting down with tremendous force and sank to the seabed with a whoosh. It was the familiar Monster Crab.

When the thirteen brave warriors saw this, they swam in from all directions and clung to the Monster Crab. A fierce battle raged in the dimly lit seabed. The Monster Crab brandished its massive claws and wildly thrashed its eight legs in an attempt to shake off the warriors, but even a monster crab stood no chance against thirteen opponents. After a long and terrifying battle, the Monster Crab finally went limp.

Like thirteen ants hauling a dead cricket, the brave warriors each pulled on the Monster Crab’s legs and rose to the sea surface.

Then, their ally’s submarine was there with its hatch cover open, lying in wait. The thirteen brave warriors climbed aboard the submarine, hoisted up the Monster Crab, and dropped it through the hatch.

About an hour later, Detective Akechi, Kobayashi, and the thirteen brave warriors returned to the deck of the Hayabusa Maru. On the deck's floor lay the discarded shell of the Monster Crab, and beside it sprawled Twenty Faces, his breath ragged and faint. There, the faces of Mr. Miyata and Kenkichi boy were also visible. Surrounding them, a crowd of sailors raised both hands high and shouted "Banzai!"

After that, needless to say, every last one of the Taiyōmaru's gold ingots came into Mr. Miyata's possession.