Pathway to Japanese Literature

The Monster of the Sunken Ship The sunken ship salvage work by Nitto Salvage Company was conducted offshore of Oto Village on the eastern side of the Boso Peninsula.

At the bottom of that sea lies the 1,500-ton cargo ship Ashikibi Maru of Toyo Kisen Kaisha. One stormy night about a month ago, the Ashikibi Maru had mistaken its course, collided with a large rock in the sea, had its hull torn open, and sank there.

The salvage company's work ship commissioned to raise this sunken vessel went to the sea surface where the Ashikibi Maru lay submerged, and first lowered two divers to the seafloor to investigate how best to perform the salvage operation. Clad in thick rubber suits, round iron helmets, and lead-weighted shoes, the two divers climbed down the iron ladder attached to the work ship's outer hull and entered the blue sea with gurgling bubbles. As the air hose delivered oxygen, the lifeline rapidly extended.

It was a rocky area in the sea resembling an underwater mountain range, with large rocks jutting upward and a bottom that proved surprisingly shallow. At just thirty meters below the surface lay the seafloor. At thirty meters down, where the sea grew as dark as twilight, the divers carried powerful underwater lamps. The electric wire was entwined with the lifeline and continued up to the work ship above. They advanced through the swaying seaweed—kelp and other marine plants growing taller than a person’s back—swinging their lamp to illuminate the way as they pushed through the fluttering vegetation.

In the distance, a dull black gigantic monster-like mass was dimly visible. That was the sunken ship. The two divers approached the black hull, swaying the air hose and lifeline behind them from their iron helmets. In front of the round glass viewports attached to their iron helmets, various fish glided smoothly past. Large sharks would sometimes appear suddenly and collide with their iron helmets.

The two men eventually reached the sunken ship and began examining the damaged area. Walking along the side of the black hull lying on its side, they moved from stern to bow while illuminating their path with underwater lamps. The sunken ship was like a massive iron house on the seafloor. They walked along that 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 found the damaged area.

The iron plates on the ship's bottom had flipped up like a giant's tongue, leaving a gaping hole large enough for two people to pass through. With water pouring in like a waterfall from such a hole, 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 peeked out briefly from inside. Instinctively, they thought there might be a large fish present, but it wasn't a fish. It somewhat resembled a human being. Moreover, what they felt wasn't an ordinary human face—it seemed terrifyingly large.

However，there should have been no human corpses remaining on this sunken ship．Because all crew members had been rescued．Moreover，what had just peeked out was not a corpse’s face．It was a living human—no，rather，something strange that resembled a human． The divers had encountered all manner of terrifying things on the seafloor and were not easily startled by minor occurrences，but whatever had glimpsed out at them now felt unnervingly sinister．Even these experienced divers began to feel afraid．

The two men stood frozen there for a moment, exchanging glances, until one fluttered his right hand before the underwater lamp's light. This served as a gestural substitute for speech. Though their diving helmets contained telephone devices for communicating with those aboard the work ship, the divers couldn't converse directly with each other. There was also a mechanism allowing communication through hand-clasping with attached wires, but such setups were rarely used.

Japanese divers had been skilled at diving to the seafloor since ancient times when advanced diving suits like today's couldn't be made, so they had grown accustomed to communicating with hand signals underwater. Just as deaf people communicate through gestures, divers too could convey anything using only hand signals. “Are you scared?” One diver’s gestures posed the question. When addressed like that, he couldn’t bring himself to say “I’m scared.”

“Scared? As if! Let’s go in and take a look.”

The other diver responded with hand gestures. “You go in first.” “No—you’re closer to the hole, aren’t you?” “You go in first.”

The two were deferring to each other about going first precisely because they were afraid. However, the bravery of Japanese maritime rescuers is known worldwide. They cannot admit to fear without betraying the honor of Japanese divers. If it became known that they had fled after seeing something suspicious, they would become the laughingstock of their comrades.

“Well then, let’s hold hands and go in together.”

“Yeah, that works.” The two of them decided to hold hands and enter the torn hole in the ship's hull.

The interior of the hole resembled a large storage room for cargo, but as the underwater lamp's light wasn't very strong, the far side of the chamber remained pitch black, making it impossible to discern what might be lurking there.

The two stepped over the edge of the hole and slipped into the ship as if floating. And so, they gradually made their way deeper inside along the severely tilted floor of the cargo hold. Crates and straw-wrapped bundles lay scattered about. Lightweight cargo had floated up and stuck to the room's ceiling. Also, something drifted gently before their eyes. In the midst of all this, large and small fish of all kinds swam around. As they approached the underwater lamp, their scales glittered beautifully in reddish gold and bluish silver hues.

These two had been divers for many years, so they had seen countless human corpses floating in such cargo holds. Bodies bloated with water, corpses reduced to mere bones—they had grown thoroughly accustomed to such sinister things. Therefore, they knew full well that the thing that had peeked out earlier was not a human corpse. Of course, it wasn’t a fish either. It was somehow an unfathomable thing. The moment they thought that thing might slither out from behind the cargo ahead at any second, even these battle-hardened brave divers felt an eerie chill creeping up their spines.

However, inside that cargo hold, there were no suspicious things visible. On one wall, the door leading from the cargo hold to the next room stood wide open. Beyond it appeared to be the engine room.

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

After discussing with hand gestures, the two men stepped through the doorway into the space beyond.

A large steam engine lay perfectly still in the stagnant water. It felt like the corpse of a machine. Even machines are alive when they're moving, so when they lie still as if dead, it feels somehow eerie. The moment the two men entered that space and took two or three steps, something truly bizarre occurred. A part of the dead machine began to clank and groan into motion.

The two men stood frozen in shock. There was no way a machine submerged for a month could start moving. Yet as they stared, part of the machinery indeed stirred to life. Before long, a mechanical component detached from the engine and drifted smoothly toward them—some spectral machine-monster. The divers screamed inside their iron helmets and fled. They thrashed through the water in desperate retreat.

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

It was a living machine. No—rather, it was a living thing resembling a machine. It had a head, two hands, and a crocodile-like tail. All of it seemed to be made of iron, like a machine.

The black iron head was about twice the size of a human's. It matched the dimensions of the diving suits' iron helmets perfectly. Two large sunken eyes glared fiercely from its face even in the seafloor's dim light. Its mouth split open to the ears, exposing sharp fangs. With thick iron rod-like arms, the monster made beckoning gestures—each iron finger tipped with eagle-sharp talons. Jagged protrusions resembling a cockscomb or animal mane ran continuously from its iron-plated torso down to its crocodilian tail. This indescribably repulsive hybrid of human and reptile stood as a grotesque fusion of biology and machinery, its entire body forged from iron.

The two divers fled through the torn hole in the cargo hold as if their lives depended on it and then, via the telephone in their helmets,

“We’re in trouble! Hurry up and pull us up!” they called out to the salvage ship. When the two divers were hauled up and told of the seafloor monster, it caused a major uproar. The next day, even the Maritime Self-Defense Force mobilized to conduct an extensive underwater search. But no matter how thoroughly they combed through the sunken ship, the monster never showed itself again. In the end, everyone concluded the two divers must have seen a phantom at the bottom of the sea.

The divers insisted, "How could that be a phantom? We saw its form clearly. What are the chances two people would see the same phantom at once?" But nobody believed them. The two divers therefore declared they would dive again to investigate and thoroughly searched the sunken ship, but never encountered the monster again.

Iron Mermaid

Sure enough, around that time, a strange thing was occurring in Ōto Village on the coast near where the diving operations were taking place.

Ōto Village was a lonely place inhabited solely by fishermen, but among the children of those fishermen was a boy named Shinada Ichirou.

His father owned a fishing boat equipped with an engine and was the best fisherman in the village. Ichirou was a first-year student at the middle school in a nearby town whose greatest hope was to become an even greater fisherman than his father and engage in deep-sea fishing. For this purpose, arrangements had been properly made for his enrollment into a specialized school. Being such a boy, he loved the sea more than anything. He swam proficiently enough to cover four kilometers with ease, and on days off found his greatest joy in boarding his father's boat to assist with fishing. When unable to sail or swim after returning from school, he maintained what had become his daily routine - gazing at the Pacific Ocean from atop a high rocky hill on the village outskirts.

All alone, he sat perched atop a rocky hill, propping his cheek on his knees, gazing fixedly—endlessly—at the sea. The vast sea, stretching infinitely all the way to the distant American continent—what a free and beautiful sight it was. Even the same sea—its beauty varied so astonishingly depending on the time that it appeared completely different. When calm as a mirror; when foaming and seething during storms that made it boil; 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 very soul.

That evening too, after returning from school, Ichirou-kun quickly finished his homework, rushed out of the house, climbed up the rocky hill, sat down at its summit, and gazed intently at the sea—that dear, vast expanse reminiscent of a giant mother.

Before long, the long clouds streaming across the great sky turned yellow, then gradually reddened until they became a vivid crimson like stained glass. This color spread across the wide sea, and as far as the eye could see, the water shone beautifully like dissolved paint. When he turned around, the bright red sun—as large as a washtub—was now beginning to hide behind the mountain behind him.

It was at that moment. Ichirou-kun suddenly looked down at the water’s edge below the rocky hill and discovered something black and strange writhing on a rock there. Startled, he strained his eyes. Since it was twenty meters below on the coast, the details weren’t clear, but there on the rock crouched something strange—something he had never seen before. “Ah! A black mermaid!”

Ichirou-kun involuntarily let out a voice. It had a form resembling a human body attached atop a fish’s tail. Its body was pitch black and jagged, but its form closely resembled that of a mermaid from some picture book. The mermaid in pictures has a beautiful naked woman with long black hair cascading down her back atop a scaly fish’s tail, whereas the mermaid now beneath his eyes was pitch-black, with a square, sturdy appearance as if made of iron. Moreover, its fish-like tail didn’t have scales gleaming silver but rather resembled a hard, imposing crocodile’s tail.

Ichirou-kun believed that something like mermaids didn’t actually exist. That a mermaid—a creature that shouldn’t exist in this world—and moreover an imposing iron-like mermaid, was now moving on the rock below his eyes made him unable to doubt his own vision. He grew frightened that something might be wrong with his head.

However, Ichirou-kun was a courageous boy. Just because he had seen something terrifying didn’t mean he was a coward who would get startled and flee. Far from fleeing, he resolved instead to get closer and clearly discern that monster’s form. Following a hidden path along the rocky hill, he hurried down and stealthily peered at the monster from behind a tunnel-like rock formation on the coast. The rock on which the monster was perched lay just about ten meters ahead of him.

The sun had completely set. The sky turned gray while the sea grew dusky black. At the water’s edge lined with rocks, white waves crashed violently. On one of those rocks sat a black iron-like creature facing away, perfectly still. The monster seen from ten meters away presented a horrifyingly dreadful sight. Crest-like protrusions along its back stood sharply pointed like arranged swords. Its massive tail resembled an iron crocodile’s, seeming ready to clatter noisily with movement.

Ichirou-kun's breathing grew harsher. Could such a terrifying monster have truly been dwelling in the Pacific Ocean? He had heard that in the deep valleys of the ocean floor dwelled monsters unknown even to zoologists—but could one of them have suddenly appeared here on this Japanese coast? Clutching his pounding chest while lost in such thoughts, the monster stirred. Then it suddenly spun around to face this direction.

Ichirou-kun felt as though his heart had leaped into his throat. Ah, that monster’s face! Ichirou-kun would never forget it for his entire life. The sharp spines on its back continued all the way up to its head. Its two large eyes—cave-like hollows—glowed with a phosphorescent blue light. Its mouth was split open up to its ears, and from between its lips, sharp fangs jutted out menacingly. The instant Ichirou-kun saw it, he concealed himself in the shadow of the rocks—but the monster had already noticed.

A loud, ominous noise—like iron scraping against iron—resounded: *Clang, clang, clang, clang...* Later, it became clear that this had been the monster’s laughter.

“Even if you hide, it’s no use.” “I know.” “Come out and listen to what I say.”

It was the monster's voice. This seafloor monster spoke Japanese. However, the pronunciation was terribly unclear, resembling the sound of iron scraping against iron—nearly impossible to discern unless one listened very carefully. Ichirou-kun thought it was all over. Convinced the monster would capture him and drag him down to the seafloor, he resolved to prepare for a desperate last stand. Then, bravely emerging from the shadow of the rocks, he glared back at the monster.

“You’re strong. Quite the impressive child.” “If it’s you, you can tell everyone what I say.” “Now listen well.” “I am the monster of the seafloor.” “Nothing remains for this village.” “But unprotected—Japan will plunge into chaos when I begin my work.” “Tell them all—the seafloor monster has finally landed in Japan.” “Understood?”

No sooner had it let out another metallic scraping laugh—"Clang, clang, clang..."—than there was a splash, and instantly, the monster’s form vanished from sight. It plunged into the sea where white waves raged.

Iron Box

Now shifting scenes to events in Tokyo.

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

In Setagaya Ward lived a second-year middle school student named Miyata Kenkichi. One night, while returning home from a friend's house by taking a shortcut, he was walking through a shrine forest. Outside was a lonely road that no one traveled at night—a path where an ordinary child would be too frightened to take such a shortcut. However, Miyata Kenkichi-kun, being a member of the Boy Detectives Club, found walking alone through the dark forest rather enjoyable.

The shrine forest stretched vast and deep, with towering trees standing in dense rows whose branches blotted out the sky—so thick that even daytime grew dim beneath them, leaving nights starless and plunged in utter darkness. Though streetlights stood scattered here and there, their glow failed to penetrate far through the leaf-choked gloom. Stone lanterns lining the path loomed like spectral giant monks, casting an undercurrent of unease through the shadows. Kenkichi-kun walked briskly through this murk, whistling as he went. Midway through the forest, he fancied he heard another set of footsteps keeping pace with his own. Pausing his whistle, he strained his ears as he walked—yes, distinct from his own footfalls came another sound. Not merely echoes of his steps rebounding through the trees, but a rapid pattering that suggested someone running.

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

As expected, someone was running up from behind.

When he whirled around, he saw a black figure darting out from between the rows of stone lanterns. It was an adult. He might be a villain. He might have been pursuing Kenkichi-kun. And he might be after his money.

However, Kenkichi-kun did not run away and remained standing motionless in the same spot.

The man instantly drew near,

“Hey you. I’ve got a request.” “An important request.” “Listen.” he said breathlessly.

“To me?” “Yeah, that’s right. I’m being chased by villains right now. Keep this for me. It’s something more important than my life. Is your house near here?” “Yes, right nearby.” “Then take this back to your house and hide it somewhere inside where no one will find it. Inside this box is sealed a terrifying 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, don’t you dare throw it away. I’ll definitely come to retrieve it, so until then, hide it somewhere no one will notice. Do you understand? For me, it’s something more important than my life. Got that?”

Amidst the darkness, as they conversed in this manner, the man’s facial features gradually became faintly distinguishable. He was wearing a black suit - a wrinkled, dirty suit. He was probably over fifty. His face bore deep wrinkles and a thick beard. This wasn’t an intentional beard growth; his cheeks had turned jet-black with stubble from days without shaving. The man with this unsettling aura was carefully holding out a small black box with both hands.

As Kenkichi-kun hesitated over whether he should accept the small box and remained silent without responding, the man kept anxiously glancing behind him,

“Hurry! “Take this.” “I’m being chased by villains.” “They could come here at any moment.” “Then 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 and—

“They’re here.” “They’ve come.” “It’s over.” “I’m begging you.” “Take this away and hide it.” “Don’t let the villains get it.” “Here, take it!” “And hide behind that large tree there.” “Don’t run away.” “They’re adults—if you run away, you’ll get caught right away.” “Listen, do you understand?”

The small box had somehow found its way into Kenkichi-kun's hands. It appeared to be made of iron and was a surprisingly heavy box for its small size. As the man shoved Kenkichi-kun's back, he staggered unsteadily and hid behind the trunk of a large tree. That spot lay in pitch-black darkness beyond any streetlight's reach, leaving no possibility of being discovered by the villains.

Once he confirmed Kenkichi-kun had hidden, the man abruptly broke into a run, though clearly exhausted and unable to move quickly. From behind came the sound of vigorous footsteps closing in. Rapid-fire footsteps—terrifyingly swift ones.

Peering out from behind the tree trunk, Kenkichi-kun saw a young man's figure materialize before his eyes, slicing through the wind. The fellow wore a garish striped suit that made him look every bit the shady character.

Instantly, he caught up to the fleeing man.

“Stop! You’re not getting away!” “I know damn well you took the iron box and ran.” “Hand it over!” At the young thug’s brazen shout, the fifty-year-old man answered weakly. “I don’t know anything about an iron box.” “Go ahead and look.” “I don’t have that thing anywhere.” The young thug began searching through every part of the fifty-year-old man’s body. But since the iron box had long since passed into Kenkichi-kun’s hands, there was no way it could materialize now.

“Damn it! You hid it somewhere. Come on, confess! Where did you hide it? If you don’t talk, I’ll make you hurt.” The young thug grabbed the fifty-year-old man’s hand and twisted it up toward his back. However, the man did not answer a single word. Not only that—now fighting with desperate strength, he wrenched his hand free and suddenly lunged at the young thug. A terrifying struggle began.

The two men 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 long, he had been pinned down by the young thug and let out a creepy groan. The young thug straddled the fifty-year-old man like a horse and was strangling his neck with both hands. The man underneath might die. He had gone completely limp and seemed unable to even make a sound.

Kenkichi-kun thought about rushing out from behind the trees to help, but even if he did such a thing, he could not possibly defeat the thug, and the iron box might be taken. If it were taken, he couldn’t face the man. Because it was a small box that he had been determined to hide even at the cost of his life, no matter what happened, he couldn’t hand it over to the thugs.

While he was busily thinking such things and hesitating, the young thug seemed to release his grip and stand up.

“I’ll spare your life.” “I’ll keep you alive until I get that iron box—the boss’ll chew me out otherwise.” “I’m heading back now to talk it over with the boss and then I’ll come back.” “We’re getting that iron box no matter what， so you’d better be ready.”

The young thug, having said such things, went off somewhere. Kenkichi-kun watched for a while, suspecting the thug might be pretending to leave while actually hiding somewhere, but when nothing happened no matter how long he waited and it seemed the man had truly departed, he timidly emerged from behind the tree and approached the fallen 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.” “It’s over.” “The box—I’m counting on you.” “When I die, throw it in the river.” “And… even if this goes to the police… keep quiet about the box.” “Don’t let them find out either.” “Don’t tell anyone in your house.” “I didn’t do anything wrong.” “Nothing that’d cause you trouble—swear it.” “Listen—promise me.”

That was all he could manage to say. The man, as he was, closed his eyes again and went completely limp.

Kenkichi-kun, realizing he couldn't handle this alone, suddenly broke into a run. He exited the shrine forest, returned to his nearby home, and reported everything that had happened to his father. He hid the iron box in the drawer of his study room's bookcase and did not tell even his father about it. His father called the police and then decided to go into the forest himself under Kenkichi-kun's guidance.

The Face in the Window

The fifty-year-old man who had entrusted the iron box to Kenkichi-kun passed away at the police hospital four–five days later.

Upon investigation, it was discovered that this man was a homeless former sailor with no family or relatives, all alone, so the police admitted him to the hospital for treatment, but as he had always been physically weak, he ultimately died.

Now that the man had died, Kenkichi-kun was supposed to discard the iron box into the river as promised. However, he simply couldn’t bring himself to throw away that container said to conceal some great secret. I wanted to quietly hide it and explore its secret myself. So, though it meant breaking my promise, I decided not to discard it yet and keep it hidden. The box was a black iron container approximately fifteen centimeters long, nine centimeters wide, and six centimeters thick, carved with a withered grass pattern. It bore no visible seams, and there was no discernible way to open it. What was inside made no sound at all even when shaken.

Kenkichi-kun felt there might be some extraordinary treasure inside, making it seem a shame to hastily break open the box. I decided to examine it properly later and needed to hide it somewhere nobody would discover. After much deliberation, he settled on concealing it beneath a suitably sized rock in the garden's artificial hill. 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, and the iron box was still there.

However, there was one thing worrying Kenkichi-kun. After the struggle in the forest, when he returned home, the knife he had placed in his coat pocket was gone. It was a small knife for sharpening pencils. While hiding in the shadow of the trees and watching the struggle, he had unintentionally gripped that knife in his hand. It wasn’t that he intended to harm the thug with it; his hand had simply moved there on its own and clenched the knife. At the time, I had intended to put it back in my pocket, but in my panic, I may have carelessly dropped it.

The knife had a deer antler attached to its exterior, but unfortunately, on the surface of that deer antler was engraved his name in Roman letters: K. MIYATA.

If that knife were found by the thugs, they might realize Kenkichi-kun was hiding the iron box. So the next day during daylight hours, he went into the forest and searched every corner of the area thoroughly, but nowhere could he find any trace of the dropped knife. Could those thugs have come back later and picked it up?

For Kenkichi-kun, that was his only worry.

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

Kenkichi-kun was at his study desk working on his school homework. It was around nine o'clock in the evening. That day as well, after confirming in the evening that no one was watching, he peered under the rock on the artificial hill and verified that the iron box remained securely in its original location. And, relieved, he was able to focus on his studies. Given how things were going, 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 occurring around Kenkichi-kun, he came to feel that everything was safe now.

However, that was not the case. Having reached a difficult part of his homework, Kenkichi-kun set down his pencil and stared into the space before him to think it through. Then, within his field of vision, there was something moving hazily. "Oh?" he thought, focusing his gaze and looking directly at it.

Beyond the desk, there was a glass window. Because the curtains weren’t drawn, the pitch-black garden beyond was visible. In that pitch-black darkness, something black was hazily moving.

Since it was something black in the darkness, he couldn't make it out clearly, but there was no doubt something was there. At first I thought it might be a person, but if it were human, its face should appear white. It doesn't seem to be human. It wasn't a human, but something of human size.

A chill ran down his spine. The black shape gradually drew closer. It came right next to the windowpane. A form became dimly visible. It was something eerie and bizarre, unlike anything he had ever seen before.

Startled, he felt his heart leap up to his throat.

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

Its forehead was sunken like a gorilla's, and from those depths peered two eyes glowing with a bluish-white light like phosphorus. Its mouth was split open to its ears, and from between those lips extended two fangs that slid outward smoothly. That was not a human face. Nor was it an animal's face. It was some unknowable thing. Its entire face shone with a black metallic luster as if cast from iron.

Kenchiki-kun tried to flee. However, when glared at by those phosphorus-like eyes - just like a frog stared down by a snake - he could no longer move a muscle, left with no choice but to remain seated in his chair, utterly still. Then, an even more terrifying thing happened. The glass window began to creak open upward from below. The monster was opening the upward-sliding window from outside.

Even so, Kenkichi-kun still did not have the strength to flee. As if bound to the chair, his body wouldn't move at all. And his eyes were drawn toward the monster; even when he tried not to look, he couldn't tear them away from it.

The window opened little by little, inch by inch upward. When it had opened about sixteen inches, the monster's face slid smoothly into the room through the window. The two eyes were burning like blue flames. On top of its head stood sharply upright an ominous crest-like object. Then its mouth... Its mouth—split open up to its ears—creaked open into a crescent moon shape, "Skraa-skraa-skraa-skraa-skraa..."

The monster laughed. It laughed with a dreadful metallic scraping sound, like iron grinding against iron.

The Monster's Whereabouts

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

“Hmm, it seems I just heard a strange noise.”

Kenkichi-kun's father came out from the back room into the dining room.

“It seems to be coming from Kenkichi’s room.” “What could be the matter?” “Could you please go check?”

Mother also stood up with a worried look on her face.

“I’ll go check.” “Toda-kun, come along with me.”

Father took along Toda-kun—the live-in student helper who had been in the corridor—and hurried to Kenkichi-kun’s study room.

“Ken-chan, did you say something just now?” Even when called from outside the door, there was no response. And inside the room, there was a strange clattering noise. “Who’s there?!”

Toda-kun, the live-in student, shouted and attempted 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 dining room.” “I’ll go get it.”

Toda-kun ran off saying that, but immediately turned back and opened the door with the key. And as soon as they glanced into the room, the two of them couldn’t help but let out an “Ah!” The boy Kenkichi was not merely collapsed. because the bookshelves and desk drawers had all been pulled out, their contents scattered across the entire room.

Father rushed over to Kenkichi-kun's side, picked him up, and called "Ken-chan! Ken-chan!" while shaking his body. Then, Kenkichi-kun finally came to his senses, opened his eyes, and suddenly clung to his father’s body.

“What happened?” “What on earth happened?” Father looked at the scattered room and open window, then asked suspiciously. Kenkichi-kun, still clinging to his father, quietly looked around the room and realized the terrifying creature from earlier was nowhere to be found. “A monster came through the window.” “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 said that and trembled violently.

Father did not believe such a monster existed in this world and suspected that Kenkichi-kun might have had a dream or seen an illusion, but it was strange that the room was in disarray as if it had been turned upside down.

Father rushed to the opened glass window and surveyed the pitch-dark garden. However, there was no sign of anything in the garden. “Oh!” Father noticed that terrifying claw marks had appeared on the window sill. They were vivid marks, as if gouged deeply by five large, sharp claws. “Hey, Toda-kun, take a look at these marks.” “Don’t these look like animal claw marks?”

“That does seem to be the case. There were no such marks until this morning. Perhaps a suspicious creature really did come in.” Toda-kun, the live-in student, 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 earlier to check on the situation—and was trembling. Father and Toda-kun left the room and headed toward the garden. When the two descended into the garden and investigated with the flashlight, they discovered that horrifying monster footprints remained in the soft soil. It was something that could only be considered the footprints of a gigantic animal with sharp claws.

Seeing such evidence, they could no longer afford to ignore it. Father immediately called the police and reported the circumstances. Upon receiving the call, the police found it strange, but since Kenkichi’s father was a prominent executive of a major company and a well-known businessman in town, they couldn’t dismiss it as nonsense. Three officers immediately sped to Kenkichi’s house by car. And they thoroughly searched both the inside of the house and the garden, but aside from the claw marks on the window and the footprints in the garden, they found nothing else.

So, deciding to investigate the exterior perimeter of the house, as the three officers were walking through the dark town beyond the wall, they spotted the figure of a man charging toward them from the opposite direction with terrifying momentum. He was running headlong as if being chased by something.

“You, what happened?”

When they called out suspiciously, the man stopped before the three.

“Ah! You’re police officers.” “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 clerk from a nearby shop—a young man wearing a jumper. “What on earth did you see?” “A monster!”

Hearing this, the officers thought this man might have encountered the monster that had attacked Kenkichi-kun and hurriedly questioned him.

“Where is this manhole you’re talking about?” “Over there. It’s just around the corner of this town.”

When the police officers heard that, they shouted "Alright!" and suddenly dashed toward that street corner. When they turned the corner, the manhole immediately came into view. However, they didn’t see anything particularly suspicious. The manhole had its iron lid securely closed. “Hey, this manhole? "There's nothing here at all, is there?"

When they asked the young man who had timidly followed, he pointed fearfully and—

“That’s it. The lid slowly lifted up, and a horrifying monster came out from inside.”

“What kind of terrifying monster was it?”

“It had fangs.” “And it had scales.” “Its eyes glowed like phosphorus.” It was indeed the same. It was the monster that had attacked Kenkichi-kun. “Maybe it didn’t come out of the manhole—it might’ve escaped into it instead.” One of the police officers looked at the manhole cover before his eyes with a truly creeped-out expression.

“All right then—let’s investigate properly.” “Lend me a hand here.” “And you—draw your pistol and keep it ready.” “If you sense danger—open fire immediately.”

The officer who seemed to be the senior among the three said this, turned on his flashlight, and crouched down beside the manhole cover. Another officer lent him a hand. The remaining officer drew his pistol from his hip holster and assumed a firing stance, prepared to shoot at a moment's notice.

“Alright, ready?”

The two police officers worked together to open the iron manhole cover and move it aside. Inside was pitch dark. The flashlight's beam suddenly illuminated the area. Was the iron-scaled monster crouching inside? No—that wasn't the case. The interior lay completely empty. The officers stood dumbfounded.

“What the... There’s nothing here at all.”

It was a sewer manhole, but since the sewer pipe was narrow, it was impossible to escape through the sewer.

The monster must have hidden inside the manhole temporarily before escaping again. What the shop clerk had witnessed earlier must have been its moment of emergence after all. This shop clerk had seen the same monster as Kenkichi-kun. With two witnesses now confirming its existence, it could no longer be dismissed as mere dream or illusion. This matter could not be ignored. Thereupon, the police officers reported the incident by telephone to their headquarters, and the headquarters subsequently contacted the Metropolitan Police Department.

From then on, there was tremendous commotion. Three patrol cars arrived. Vehicles came in numbers from the Metropolitan Police Department and local police stations. And newspaper reporters. Kenkichi-kun's house became the temporary investigation headquarters, with more than ten vehicles lined up before the gate, and as neighbors gathered to see what was happening, it instantly became a sea of people.

A large-scale search by dozens of police officers began. Every nearby house was systematically searched, every town patrolled by police cars, emergency lines established, and an investigative net spread so thoroughly that not even an ant could slip through.

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

The newspapers of that day were filled with articles about the iron-scaled monster. The claw marks left on the window frame of Kenkichi-kun’s house and the large animal footprints in the garden were photographed and featured in the newspapers. People all over Japan read that newspaper and shuddered in terror. And wherever people gathered, their conversations were dominated by talk of this terrifying monster.

Large Gold Bullion

Kenkichi-kun waited until the police officers had withdrawn the next morning, then slipped out into the garden. It was to check that small iron box he had hidden under the garden stone. He was unbearably worried that last night’s monster might have taken the iron box. When he lifted the marker stone—ah, good. The iron box was there. It had remained exactly in its original spot. Kenkichi-kun thought he could no longer keep it hidden by himself. So he took out the box, hurriedly rushed into the house, showed it to his father, and explained in detail: how during that night’s struggle in the shrine forest, a dirty, bearded man had entrusted him with this box; how the man had said to throw the iron box into the river if he died; but even after the man died at the police hospital, he couldn’t bring himself to discard it and had buried it under the garden stone instead.

His father tried to take the iron box and open it, but he couldn't open it no matter what. Toda-kun, the live-in student, also tried, but he still couldn't manage it either.

At that moment, Kenkichi-kun suddenly seemed to have an idea and spoke up in a cheerful voice. “I have a good idea. I’ll take this box to Detective Akechi’s office and show it to Leader Kobayashi of our Boy Detectives Club. And if we borrow Detective Akechi’s wisdom, we’ll surely uncover this box’s secret.”

“Hmm, that’s a good idea. Have Toda-kun accompany you and take the usual hired car we always call. With both the driver and Toda-kun as escorts, it should be safe enough. Plus, it’s broad daylight after all.” Since Father had approved, they first called Detective Akechi’s office and confirmed both the detective and Kobayashi Shōnen were present. After summoning their regular driver’s car, Kenkichi-kun carefully cradled the iron box and boarded it together with Toda-kun, the live-in student.

When they arrived at the office, Kobayashi Shōnen came out and ushered the two into the reception room. After listening to Kenkichi-kun's account and taking hold of the iron box, he tried various approaches, but even Kobayashi Shōnen couldn't open it.

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

Kobayashi Shōnen said that and left through the door carrying the box, but after about ten minutes, he returned smiling together with Detective Akechi.

“Detective Akechi opened it without any trouble.” “See? Like this.” “It’s the same as a Hakone woodwork secret box.” “Press the hollow grass pattern here.” “Then this side will open.” “Then press here.” “Just repeat the same process two or three times.” “Then it opens completely.”

"But there's something even more significant than that. Inside this box had been something worth tens of billions of yen."

While they were still astonished by Kobayashi Shōnen’s explanation, Detective Akechi sat down in a chair and began speaking with a smile. “It’s like this.” “Inside this iron box were sealed three written documents.” “One was the will of a man named Fukunaga, who had been captain of the ocean liner Taiyō Maru.” “Another was a nautical chart of the waters south of the Kii Peninsula.” “The third was the insurance company’s document.”

Akechi said this and showed several written notes he had been holding in his hand. “Now, the former captain’s will is written in rather complex language, so to break it down for you: About twenty years ago, a steamship called the Taiyō Maru sank in a storm off Shionomisaki in the Kii Peninsula.” “It was a once-in-decades storm so severe that even when the Taiyō Maru sent wireless distress calls, they couldn’t dispatch rescue ships from shore—so many passengers and crew members perished.”

Clinging to drifting boats and finally reaching the shore were over a dozen crew members, among whom was a man named Captain Fukunaga. "A captain who only saves himself isn't much of a great captain." When the Taiyō Maru sent a wireless distress call, it naturally reported its current position, but Captain Fukunaga’s will states that in his panic at the time, he made a grave error. Because he had mistakenly relayed the longitude coordinates to the wireless operator, the Taiyō Maru later appeared to have sunk in a completely different location. After the insurance company paid the insurance money to the shipping company and investigated the sinking site, they discovered it was at an extreme depth where not only the ship but even its cargo couldn’t be salvaged, leading them to abandon the effort.

Captain Fukunaga reportedly realized about a year later that the sinking position he had transmitted via wireless was incorrect—isn't that strange? The captain may have deliberately chosen not to notice. Then after about another year had passed, he purchased the rights to the sunken Taiyō Maru from the insurance company. In the money of that time, it was something over 200,000 yen—in today's terms, about 100 million yen. He raised that money and claimed the sunken ship as his own. Since it was a ship that couldn't be salvaged anyway, the insurance company sold it off cheaply.

The reason he spent such a large sum on a ship with no prospect of salvage was that the vessel was loaded with gold bullion being sent from Hong Kong to America. “The will stated its value at four million yen back then, which would amount to about two billion yen today.” “The captain tried to salvage it and become wealthy.” “Since he had already purchased the rights from the insurance company, there was no need to hold back from anyone.”

The insurance company had sold the rights believing no diving technology worldwide could salvage from such depths, but Captain Fukunaga had known full well that the Taiyō Maru actually lay sunk in shallower waters—five miles from its reported wireless coordinates. "He must have calculated salvage operations would be feasible there." As he made final preparations to commission a salvage company for recovering the gold bullion, Captain Fukunaga fell gravely ill, became incapacitated, and died within three months. "Divine retribution caught up with him, I suppose." "Therefore, while still able to write, he drafted this will, had an iron secret box crafted to seal inside both the insurance documents and nautical chart marking Taiyō Maru's true resting place, then left it to his sole heir."

That son was the one who entrusted the iron box to Kenkichi-kun. This son was a spineless man who couldn’t even begin salvage operations himself. He tried pushing the salvage rights onto several wealthy individuals, but by then he had grown poor and appeared disreputable—no one would believe such a man’s story about “Great Gold Bullion of the Seafloor,” like something out of a dream. And before anyone knew it, twenty years had passed. “That matter has been written at the beginning of the will in the son’s own hand.”

Detective Akechi’s lengthy explanation had finally come to an end. To Kenkichi, there were still parts he didn’t fully understand, but regardless, the fact that two billion yen worth of gold bullion remained sunk off Shionomisaki somehow began to take on a sense of reality.

Daytime Monster

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

“The one targeting this small box is a terrifying villain.” "Sending it to Kenkichi-kun’s home is worrisome enough." “However, I will protect it.” “Everything’s secure, so return home without worry.” “And hide it back under the original stone, okay?” Having said that, he went to the desk in the corner of the room, put the written note into the small box, closed the lid as before, and handed it to Kenkichi-kun.

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

The car began heading toward Kenkichi-kun’s home in Setagaya, and after about fifteen minutes, it came upon a deserted road lined with large estates. On both sides, high concrete walls continued for a hundred meters; inside those walls stood large trees, making it dim even during the daytime.

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

“What a strange place to stop.” “What’s wrong?” “Did something break down?” Toda, the live-in student, called out to the driver. Then the driver—who had been facing forward—swung around abruptly and gave a sly grin.

“Ah! You’re not the same driver as before!” “When did you switch places?” “And who the hell are you?!” “That’s how it works.” The driver answered in a brazen voice and thrust his pistol forward with a sharp motion.

“Ah! Then you’re…” Toda startledly pulled Kenkichi into a protective embrace. With the opponent holding a pistol, there was nothing he could do. “Now now—I’m not saying I’ll take your lives.” “Just hand over the iron box.” “Hurry up and give it here.”

Toda, if there was an opportunity to jump out of the car and escape, quietly placed his fingers on the door handle. Then, the opponent, having already anticipated this, laughed mockingly.

“Hahaha… No, no. Even if you try to escape, there’s no way you can.” “Take a good look outside the door.”

Startled, he looked outside the glass window. There stood a man with a terrifying face right beside the pane—how had he appeared without them noticing? In his hand was a pistol held at ready, its bearer smirking all the while. Then when he looked from this side to the opposite window—what now? There too glared another ruffian of similar ilk aiming his own pistol straight at them!

With pistols aimed at them from three directions, there was nothing more they could do. Toda signaled to the boy Kenkichi with hand gestures to pass the iron box. Kenchiki-kun also had no choice but to hand it over to the previous driver.

The opponent snatched it up as if grabbing stolen goods, then laughed mockingly once more.

“Bwahahaha... Impressive, impressive! You lot really know how to obey orders.” “Well then, I’ll let you off easy this time.” “Your driver’s crammed into the trunk.” “Once we’re gone from sight, go ahead and pop that trunk open to free him.” “That way your chauffeur here can drive you again.”

The fake driver jumped out of the car and slammed the door shut with a thud. And then, the three men dashed off toward the other side with terrifying speed, like sprinters.

“Ah! I’ve done something irreparable! That important iron box has been taken. Ken-chan, they’re the henchmen of those criminals from before…… Still, Detective Akechi had assured us it’d be safe since I’d protect it—what on earth happened? If it gets taken this quickly, even Detective Akechi can’t be relied on. That’s truly disappointing.”

Toda continued muttering resentfully, but once the three men had disappeared from view, he got out of the car after a while and opened the trunk lid. There lay the familiar driver, gagged with a cloth, curled up and crammed inside.

Kenkichi-kun also got out of the car and helped. And after pulling him out of the trunk and removing his gag, the driver, while rubbing his head, “When I parked carelessly in front of Detective Akechi’s office, someone suddenly struck me hard from behind here and forced this gag into my mouth.” “He was frighteningly strong—I couldn’t do a thing.” “I’m terribly sorry.” “So that guy disguised himself as me and drove all the way here.”

“That’s right.” “Since he was wearing a jacket just like yours, we couldn’t tell you apart from behind.” “No one would have expected them to pull off such a bold stunt in broad daylight.” “Alright, hurry up and drive.” “Since we’re almost home anyway, let’s call the police once we get back.” “We’ve had the important thing stolen.”

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

Something was peering down from the top of the high concrete wall. Behind it, large tree branches grew thick in a bluish-black tangle. Atop the wall before it, something black came into view. It was an indescribable, bizarre thing. Within its black face burned two eyes glowing blue like phosphorescent fire. A mouth split open up to the ears gaped wide. From that maw jutted white fangs sharp as blades. Upon its head 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 fixedly at them. “Hurry, hurry...” Kenkichi-kun had encountered it once before, so he knew full well how terrifying it was. As if the monster would leap over the wall and come chasing after them at any moment, he urged the driver on. The driver, thoroughly frightened by this terrifying monster, suddenly accelerated. The car charged through the deserted valley town like a madman.

*Hayabusa Maru*

When Kenkichi and the others returned home, they jumped out of the car and rushed into Kenkichi’s father’s room. They caught their breath and relayed the recent events.

His father immediately called the police to report this incident and then contacted Detective Akechi’s office. “What? The iron box was taken? I thought as much.”

Detective Akechi on the other end of the line, having said that, seemed to ponder for a moment but quickly continued speaking.

“Then I’ll come over to your place right away.” “There are things I can’t discuss over the phone.” “However, please rest assured.” “I promised Kenkichi-kun that I would definitely protect him.” “I am properly keeping that promise.” Then the call ended, but what on earth had Detective Akechi been talking about? Wasn’t the promise to protect the iron box? That iron box had long since been stolen. What could he possibly intend to do now at this late hour? Father tilted his head quizzically.

Before long, Detective Akechi came rushing over by car. Father and Kenkichi-kun ushered Akechi into the parlor and entertained him.

"I didn’t fully understand our earlier phone conversation, but it sounded like you said you would protect the iron box at all costs." Father asked Akechi accusatorily.

“That’s correct. I am indeed protecting it.” The famous detective answered with a beaming smile. “What? How on earth does that work? The iron box has been taken by the villains, you know.”

“Not at all, there’s no need for concern. Only the box was taken. The contents are right here.” Akechi took out a large envelope from his pocket and showed them the captain’s will, nautical chart, and insurance company certificates from inside it. “Ah! Then, Detective...” “That’s right. Anticipating such a possibility, I had swapped out the contents of the box. 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, since I didn’t realize that was the situation, I ended up acting rudely.” “Please forgive me.” “As expected of Detective Akechi.” “With this, I am completely relieved.”

Father kept expressing his gratitude over and over. Akechi chose his words anew, “Mr. Miyata, there’s no telling what schemes the villains might attempt next. How about we quickly salvage the gold bullion on our end? What is written in the will cannot be false. After Kenkichi-kun returned earlier, I conducted some research, and it is certain that twenty years ago off Cape Shio, the Toyo Steamship Company’s Taiyō Maru did indeed sink. Moreover, it is undoubtedly true that at that time, they attempted to perform salvage operations but were unable to do so.”

"It’s worth attempting. How about consulting with Toyo Steamship Company and the insurance company to have them cover the costs? Then, if gold bullion is found, we could agree to divide it between you, the steamship company, and the insurance company. We should notify the government too and explore the seafloor." Kenkichi’s father remained silent for a while, deep in thought, but eventually spoke with resolve.

“Well then, let’s give this seafloor adventure a try. Fortunately, I have friends among the executives of this steamship company and the insurance company, and I also have a close contact at a salvage company that salvages sunken ships, so 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 details about salvaging the gold bullion, a phone call came. When Father stood up and went to put the receiver to his ear, a strange noise came through. A sinister clanging sound, like iron being scraped together. He thought it might be a phone malfunction, but it wasn't. Something was being said.

“Akechi’s there, right? I have matters to discuss. Summon him.” The sound defied human voice recognition – an eerie metallic rasp. “Who are you?” “Akechi’s... associate. Summon him. Now.”

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

“I am Akechi. Who are you?” “You know me. Your enemy. I concealed what lay within that box you coveted. Mark my words—I shall reclaim it. Akechi—remember.” With a metallic clang, the call ended. Akechi locked eyes with Kenkichi’s father.

“It’s the Iron Mermaid. As expected, that thing is after the large gold bullion. We mustn’t lower our guard. We must begin salvage operations immediately.”

After that, about two weeks passed without incident.

And then one day, the Hayabusa Maru of Nitto Salvage Company departed from Osaka Port toward Cape Shio.

Hayabusa Maru was a six-hundred-ton salvage vessel. In addition to engineers, divers, and crew members from the salvage company, Kenkichi-kun, his father Mr. Miyata, and Kobayashi Shōnen boarded this ship. They came by train from Tokyo to Osaka and boarded this ship. Kobayashi-kun accompanied them as Detective Akechi’s representative. And it was agreed that if any difficulties arose, they would notify Detective Akechi via wireless.

It was spring. The sky stretched clear and blue above the sea smooth as a tatami mat as Hayabusa Maru glided forward. It was a pleasant voyage. Kobayashi Shōnen and Miyata Kenkichi went up to the upper deck and stood shoulder-to-shoulder watching the foaming white wake at the stern while singing in resounding voices.

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 foil across its entire surface.

Except for crew members standing watch at their posts, everyone had entered their cabins and gone to sleep. The thudding rhythm of engines and whooshing sound of waves being cut—under that moonlit brilliance—left no other noises remaining. A sailor walked across the deck with clomping steps. This was his hourly patrol. He passed through a narrow passageway beside central cabins and emerged toward the bow. Passing beneath hoisted lifeboats and glancing over, he saw a black mass crouching at the bow's very tip.

“Oh? Is someone sleeping over there?” Thinking it strange, he approached closer, but it didn’t seem human at all. Its entire body was covered in large scales that glittered under the moonlight. It had a long tail. From its head down to its back ran something like a jagged crest. The thing looked somewhat like a large crocodile. However, crocodiles weren’t supposed to live in these waters.

The sailor felt a chill creep down his back. It was a bizarrely unsettling creature unlike anything described in any animal book. But driven by morbid curiosity, he continued creeping closer—and then the black creature raised its head and slowly turned toward him.

When he caught sight of it, the sailor’s body went numb, rendering him unable to flee or cry out. The large face resembling black iron had sunken eyes that glowed like phosphorus. From its crescent-shaped mouth split up to the ears, white fangs slickly protruded. “Clang, clang, clang, clang, clang…” The monster opened its mouth wide and laughed. The laughter was an eerie sound, like iron scraping against iron.

“Aaaah!” Finally, a voice came out. The sailor mustered a life-or-death voice and called for help.

“Someone, help...” At that cry, running footsteps echoed from somewhere as sailors came rushing over—first one, then two, then three. The monster at the bow laughed with an especially raucous voice before swiftly twisting its body around. Its scales glittering, it cleared the ship's railing and plunged into the sea with a thunderous splash. Hurrying to the ship's side and peering down, they saw an iron crocodilian creature swimming parallel to the vessel—only for it to dive deep underwater and vanish from sight in an instant.

It was the Iron Mermaid. Having failed to steal the nautical chart from the iron box, it must have secretly pursued Kenkichi-kun and the others, tracking them to this ship. Even though it had plunged into the sea, that thing was fundamentally a creature of the depths. It might have been swimming at the same speed as the ship. And it might continue chasing after Kenkichi-kun and the others relentlessly.

The Cabin's Skeleton Kobayashi Shōnen reported this incident via wireless to the Tokyo Metropolitan Police Department and had them relay it to Detective Akechi’s office. After that, with no further incidents occurring, Hayabusa Maru arrived off Shio-no-Misaki Cape. The nautical chart obtained by Mr. Miyata clearly marked the latitude and longitude where Taiyō Maru had sunk, so surveying that section of seafloor with a sonar device would suffice. A sonar device works by emitting ultra-short waves from a ship that strike the seabed and return, their travel time converted into a graph appearing on paper. These graph curves indicate sea depth, but should a sunken ship be present, only that area would bulge into a sudden line on the display - allowing for identification.

Hayabusa Maru repeatedly crisscrossed the sea area marked on the nautical chart, examining the sonar device's graphs each time. They confirmed that the bulge in the curve was undoubtedly a sunken ship rather than seafloor rocks or anything like that. From the sea surface to the upper part of the sunken ship measured merely about thirty meters. This depth meant they might salvage not just the gold bullion but potentially even the Taiyō Maru itself. Because the Taiyō Maru's captain had concealed the true sinking location, precious gold bullion and iron materials had lain dormant on the seafloor for twenty years.

Once the sunken ship's location was determined, they finally decided to deploy the divers. Since even the captain's will made no mention of where the gold bullion had been stored aboard Taiyō Maru, merely locating it would prove a formidable task. Therefore, this dive wasn't about immediately salvaging the gold bullion—it was first to confirm whether the sunken ship was indeed Taiyō Maru.

That day dawned with a sky stretched clear and blue—fine weather indeed. With neither wind nor waves, it proved ideal for diving.

The salvage company personnel selected two skilled divers, dressed them in rubber diving suits, put brass diving helmets on them, and prepared the air supply engine to send air into the helmets. The two divers descended the vertical iron ladder attached to Hayabusa Maru’s outer hull, shaking their round, octopus-like heads as they dragged their lifeline, a rubber hose-like air supply tube, and the telephone line coiled around it into the frigid water.

On the ship, among the captain, steamship company personnel, and Mr. Miyata—the director of this salvage operation—Kenkichi and Kobayashi Shōnen watched intently as the divers, their bizarre forms sinking into the sea. The two divers held something like an iron rod in their right hands for prying things open, while in their left hands they carried underwater lamps to illuminate the dark interior of the sunken ship. The divers rapidly sank through the water by means of large lead weights attached to the soles of their feet and hung from their chests. As they sank, the enormous hull of the ship came into view from below. Having been submerged for twenty years, debris had accumulated in the water, seaweed grew from it, and countless shells adhered to the surface, making the iron ship appear more like a massive undersea rock formation than a vessel. The hull had sunk at a sideways tilt of about thirty degrees. The deck was tilted like a steep slope. The two divers had descended near the bow of the sunken ship. They reached the outer side of the bow, scraped off shells and other debris with iron bars, swung their underwater lamps around to illuminate the area, and searched for where the ship’s name was written. And without difficulty, they confirmed that it was undoubtedly the Taiyō Maru.

Then, the two divers clambered up the tilted deck and searched for the hatch (an entrance leading from the deck into the ship's interior). That too was soon found, so they descended the narrow stairs from there and entered the lower cabin. The iron stairs were completely covered in shells, making it feel as though they were entering a rocky cave. At the bottom of the stairs was a large room. No—rather than a room, it was a vast cavern. On the slanted floor lay twenty years' worth of accumulated debris, from which kelp-like seaweed grew as high as a man's chest—so dense that walking became nearly impossible.

This was below the upper deck where valuables like the strongroom were located, so the divers had descended to search for it—but with walls completely covered in shells making it impossible to discern any doors, there remained little hope of locating the gold bullion. Since the cabin floor was also tilted thirty degrees, they slipped and slid with every step in their lead-weighted shoes. However, unlike on land, even when slipping there was no risk of falling. This was because their bodies were buoyant underwater.

When their feet slipped, debris that had accumulated up to ten centimeters around the seaweed roots billowed up before their eyes, obscuring their view. Moreover, fish that had been hiding among the seaweed began fleeing in schools. As they passed through the beam of the underwater lamp, their scales shimmered gold and silver, creating a truly beautiful sight. The divers wore rubber diving suits up to their wrists but had work gloves on their fingers. This made their work easier. One of the divers slipped on the tilted floor and planted his hand in the sludgy debris. Then his hand touched something strange and hard.

“Hey, it’s a Buddha statue.” On land, they could have said that to alert their companion, but in diving suits, they couldn’t speak to each other at all. He shook the underwater lamp two or three times sideways to signal “look here.” Then he picked up a hard object from the debris and held it up before the lamp. It was a skull—black cavernous eyes and a row of clenched long teeth. Though accustomed to skeletons in sunken ships, the divers still found this eerie. Then the other diver extended his hand into the lamp’s light. That hand was gripping a leg bone of the skeleton.

Then, when they brought the underwater lamp closer to the debris on the floor and searched around, hands, feet, and rib bones began to appear one after another. The crew members of the Taiyō Maru had died in this room. That had now been reduced to nothing but scattered bones. Monster! Monster!

The two divers found the bones eerie but weren't truly scared. They were strong, robust young men—not cowards to be startled by trivial matters. Yet something occurred that made even that brave diver tremble violently, overwhelmed by terror.

As the two divers attempted to advance deeper into the wreckage after finding the skeletal remains, they noticed faintly illuminated seaweed swaying gently ahead through their underwater lamps' glow. The surrounding seaweed had swayed with their movements all along, but this distant shifting felt unnatural. Could some large fish be hiding there? That stretch of sea teemed with sizable marine life. Astonishingly huge crabs also inhabited those depths. Half-amused by anticipation of what might leap from behind the seaweed curtain, they pressed forward while sweeping their lamps across the murk.

When they looked, from between the swaying kelp-like seaweed emerged a dark object. It might be a crab's leg. Yet even so, it was a dreadfully large and thick leg. The blackish leg-like object had its tip split into several parts that bent sharply. Each segment bore sharp claw-like protrusions. It looked exactly like human fingers. But could such black human fingers exist?

The divers froze there. They had grown frightened somehow. The black arm stretched forcefully forward, a black shoulder emerged, then a face-like object abruptly peered into view. When they saw it, they gasped "Ah!" inside their diving helmets.

Two enormous eyes glowing with a phosphorus-like pallor; a terrifying mouth split open to the ears; from that mouth protruded two white fangs, jutting out sharply. And atop its iron-black head were sharp, pointed serrations resembling a cockscomb. The divers had never actually seen the Iron Mermaid before. However, they had heard stories about it lying sprawled on the Hayabusa Maru's deck. This creature could only be that very Iron Mermaid. True to form, the monster had trailed the Hayabusa Maru all the way to Cape Shionomisaki. And now it had already infiltrated the Taiyō Maru's cabin.

As the divers trembled and tried to flee, the monster revealed its entire body and suddenly lunged toward them. Ah, the sheer terror of it! The motion resembled a locomotive charging forth in a film. Two glowing blue eyes and white fangs came barreling through the water as if leaping straight at them. "A mermaid!!" "It's the Iron Mermaid!! Pull us up! Hurry up and pull us up!"

The divers shouted at the top of their voices inside their helmets. Their voices were transmitted via telephone line to the Hayabusa Maru above, of course. Struggling, they tried to flee from the ship's cabin. The monster extended its horrifying hand from behind them and closed in.

The diver who had lagged behind had his leg seized in an instant. Five sharp claws sank deep into the diving suit. He was now locked in a life-or-death struggle. Swinging up the iron rod in his right hand, he pounded wildly at the monster, thrashing desperately until at last he wrenched his leg free.

And so, both of them managed to float up from the ship’s cabin to the hatch. For some reason, the monster did not pursue them that far.

Fish-shaped submarine

When the divers returned to the Hayabusa Maru and reported about the monster, the ship was thrown into an uproar. Mr. Miyata and the other key members hurriedly gathered in the captain’s cabin and began their discussions. "As I thought, it followed this ship." "It must intend to steal the gold bullion." "We have to find a way to stop it." Mr. Miyata said worriedly with a pale face.

Then the captain nodded. "We can't handle such a monster on our own." "Depending on circumstances, we may have to request help from the Maritime Self-Defense Force." "Our only option might be to blast cannons into the ocean to kill it." "In any case, I'll radio headquarters for instructions." "And have them send reinforcements from Osaka." Then the salvage company engineer seated there spoke up.

“Even so, this is taking too long. The monster may have already found where the gold bullion is hidden. If it gets stolen, we’re finished... Captain, why don’t we try using that?” “The Diving Bell?” “That’s right. I’ll go inside it and keep watch over the monster. No matter how powerful the Iron Mermaid might be, it won’t stand a chance against that machine.”

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

A Diving Bell was a diving machine shaped like a large sphere made of thick iron. A person would enter inside it, and it would sink to the seabed. The iron sphere had thick glass windows, with powerful underwater lights resembling searchlights mounted above them that allowed clear visibility into the sea. Additionally, the iron sphere had two iron arms whose tips formed large claws for grasping objects. They were iron claws.

The salvage company used this diving machine for deep-sea work at depths where divers couldn’t reach, but the Captain had brought the machine aboard considering every possible contingency. The Hayabusa Maru was equipped with a small crane (winch) for handling the heavy diving machine. Several crew members operated the crane, using wire ropes to hoist the diving machine from the hold, and the engineer entered inside it. After sealing the machine, they changed the crane's direction, extended it over the sea surface, and slowly lowered the diving machine into the sea.

The interior of the diving machine was arranged like an airplane cockpit, allowing everything to be done while seated. In front of the seat were numerous buttons; pressing them allowed free movement of the external iron arms and claws. The engineer stared intently at the sea through the glass porthole. The machine steadily descended. Under the strong light from the lamp above the window, everything up to ten meters ahead could be seen clearly. In that light, the sight of fish of all sizes swimming left and right was truly beautiful.

The diving machine would not enter inside the sunken ship’s hatch, so it was meant to go near the hatch entrance and keep watch there. As he looked out the window, the sunken ship on the seabed gradually grew larger. In other words, it was approaching. "Oh! That’s a terrifyingly huge fish!" The engineer involuntarily muttered to himself. From far beyond the reach of the electric light, he saw a huge fish—something like what one might call a baby whale—approaching from the distance.

While whales weren't unheard of in these waters, this creature differed entirely from any known whale. What struck him as particularly strange were its terrifyingly large eyes that blazed like car headlights. Though its eyes resembled those of a killifish in proportion, its body measured tens of thousands of times larger than the tiny fish. Could such an absurd creature truly exist? As he wrestled with these thoughts, the gigantic fish drew steadily closer. Not only were its eyes enormous, but its mouth formed a perfect circle like those on Children's Day carp streamers. Stranger still, the mouth remained completely motionless. The light from its eyes intensified further until the water ahead suddenly brightened as if struck by searchlights. Attached to the monster fish's back was something resembling a transparent air sac—a flat, membranous pouch.

“Th-that’s no fish! It’s a submarine! A fish-shaped submarine!” The engineer involuntarily let out a shrill cry. It was indeed made of iron. What had appeared as two eyes were indeed the submarine’s headlights. That round mouth might actually be the muzzle of a cannon. Even so, which country could this bizarre submarine have come from? No—it wasn’t from any country. This must certainly have come from the devil’s country.

Underwater Showdown

"Oh! There's something strange here. What on earth is that?" The engineer was startled and stared at the submarine's back. The light from the two glowing eyes at the front was so intense that the rear area remained poorly visible, but there, crouching in that dimness, was something terrifying.

It was the Iron Mermaid. An iron face, an iron crest, two fangs jutting sharply from a mouth split open up to its ears—its body was that of a crocodile-like monster. It clung flatly to the back of the fish-shaped submarine like a gecko, its glowing blue eyes staring fixedly in this direction. Though protected inside the iron sphere—safe from any monster's approach—the Engineer found himself frozen in fear at the Iron Mermaid's horrifying visage, a chill running down his spine.

The fish-shaped submarine came right into view. While they could move freely, we were suspended by a rope from the Hayabusa Maru—there was no way to escape. The engineer grabbed the telephone inside the diving machine and shouted. “Hurry up and pull me up...!” “A terrifying submarine has arrived.” “On its back...the Iron Mermaid is riding...” “What? A submarine?” “Is that true?!”

The voice of the Hayabusa Maru's captain came back in response. "That's right! It's a terrifying fish-shaped submarine! It’s right in front of us now! Dangerous! Hurry, hurry—pull me up!" Then aboard the Hayabusa Maru, they seemed to have begun the retrieval operation, and the diving machine started rising gradually upward. At that moment, something shocking happened. From the round mouth-like opening of the fish-shaped submarine before them, a long black rod resembling a snake’s tongue suddenly shot out. The tip of the rod split into two parts, forming a clamp-like structure. Then this clamp extended toward the upper section of the diving machine where the engineer was stationed.

The engineer hurriedly peered through the small glass window that was open above. Ah! The monster's iron clamp was trying to grasp the rope suspending the diving machine—wasn't it? "It's terrible! The enemy is trying to cut the rope! Hurry, hurry! Pull me up faster, much faster!"

Aboard the Hayabusa Maru, they spun the rope retrieval engine even faster. With that force, the diving machine lurched violently and seemed about to collide with the fish-shaped submarine directly above. The engineer frantically spun the handle in front of him. Then, the iron arm protruding from the diving machine moved forcefully left and right, slamming into the submarine’s flank. The Iron Mermaid clinging to the submarine’s back forcefully stretched its neck toward them and glared with phosphorescent eyes.

The engineer clattered the handle again. The iron arm extended toward the monster and nearly seized its crocodile-like tail. It was a dreadful grappling between the submarine’s iron tongue and the diving machine’s iron arm. A battle of machine versus machine. The seabed water swirled into vortices and frothed, fish scattered in panic, the round iron diving machine swayed violently, the submarine thrashed its tail left and right to avoid releasing the rope, and atop its back, the Iron Mermaid thrashed about—this life-or-death struggle continued unabated.

However, in the end, the Hayabusa Maru's winch proved stronger than the iron clamp's force. The rope was rapidly reeled in, and the diving machine wrenched free from the iron clamp to be hauled up toward the sea surface. The engineer who emerged from the diving machine and climbed onto the Hayabusa Maru's deck was drenched in sweat from head to toe, his face flushed crimson as sweat streamed down steadily. After catching his breath, he gave a detailed account of the underwater battle's progression to the captain, Kenkichi-kun's father, and the others.

“I never imagined the enemy would have a submarine,” “The Iron Mermaid has numerous companions.” “We stand no chance like this.” “While we’re stuck with this cumbersome diving machine, they’ve got a submarine roaming freely across the seabed.” “We’ve finally reached the point where depth charges are our only option, haven’t we?”

There was no choice left but to request support from the Maritime Self-Defense Force. The captain sent a wireless message to the Osaka branch office and informed them of the situation. Then, in response to that, a wireless message came back from the branch office—one that would astonish everyone. “Detective Akechi, armed with powerful weapons, departed this morning. Expected to arrive there at 5 PM.”

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

Detective Akechi Arrives

When they said 5 PM, it was still a little over an hour away. Everyone remained standing on the deck, waiting for the ship carrying Akechi to arrive. “What exactly are these ‘powerful weapons,’ I wonder. No matter how great a detective he is, he probably didn’t know the enemy had a fish-shaped submarine. So I’m worried whether he’s bringing weapons that can defeat that thing.” The captain was whispering such things to the engineer. Even when they inquired by wireless, they wouldn’t answer anything about the weapons.

Meanwhile, Kobayashi and Kenkichi were talking with bright expressions.

“Kobayashi-san, that’s Detective Akechi for you! Yesterday, when he learned through the wireless message you sent from this ship that the Iron Mermaid was following, he immediately went to Osaka, right? He must have taken a plane. And he departed Osaka Port early this morning, right? But still—what could these ‘powerful weapons’ be?” “I don’t know either. Detective Akechi always thinks far ahead of us. That’s why when he took on this case, he might have already properly prepared the weapons. It’s all right now. If Detective Akechi comes, it’s as good as done.”

Kobayashi-kun said cheerfully, his face breaking into a smile. Before long, a thin trail of smoke became visible far beyond the horizon, and peering through binoculars revealed the small form of a white steamship emerging there. It was an express ship called the Kamome Maru from the shipping company. This regular passenger ship that passed through Shionomisaki was an extremely fast vessel, and they had learned via wireless that Akechi would be coming aboard it. The Kamome Maru, its hull painted pure white, rapidly grew larger as it approached. The people on the deck of the Hayabusa Maru waved handkerchiefs and shouted "Banzai!" to welcome 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 and gazing over at us. They must have heard the rumors about the gold bullion salvage.

The lowered boat, with four sailors rowing oars, approached straight toward us. A *Banzai* cheer resounded across the Hayabusa Maru's deck. Standing tall in the boat was our renowned detective, Akechi Kogoro. His tall frame was clad in a well-fitted black suit, his unruly hair fluttering in the wind as he raised his right hand high in greeting. “Oh! What is that?” “Something like a sea monster is coming!”

Someone shouted. When they looked, a large black monster was approaching from behind the Kamome Maru, following the boat's wake—a whale-like black creature with a massive hump on its back. Upon closer inspection, something resembling a thin iron rod protruded from the hump. Kobayashi-kun cried out: "Ken-chan, that's a periscope! It's the viewing scope submarines use to see above water from below. So that thing's a submarine! Whoa, awesome! Our submarine has arrived!"

“It’s true.” “We’re safe now, aren’t we?” “That will take care of the enemy’s fish-shaped submarine.” “Hey Kobayashi-san, Detective Akechi is amazing, isn’t he?”

The two boys jumped up and rejoiced. The people on the deck were also in an uproar upon hearing that their submarine had arrived. Once again, cheers of "Banzai!" welled up.

Before long, the boat came alongside the Hayabusa Maru, and Akechi climbed the iron ladder to appear on the deck. While putting his arm around Kobayashi-kun's shoulder as the boy clung to him, he exchanged greetings and reports with Kenkichi-kun's father, the captain, and the engineer. A crowd of sailors surrounded them in a circle, gazing in awe at the famous detective.

“I see.” “Did the enemy also have a submarine?” “I hadn’t considered that far ahead, but since I thought a submarine would be essential to defeat the Iron Mermaid, I had prepared one from the very beginning.” “While Japan no longer has submarines like those formerly used by the navy, I learned that a small civilian sightseeing submarine for undersea tours was stored at Toyo Steamship Company. So I had it overhauled and kept ready for immediate deployment.” “Though this type of submarine cannot launch torpedoes, its form resembles a navy submarine scaled down exactly.” “It’s fully adequate for intimidating the enemy.”

“Since the submarine had been relocated from Kobe to Osaka Bay, I had the Kamome Maru tow it here.” After some discussion, Akechi laid out the following plan.

“That submarine has two skilled operators aboard. After thoroughly instructing them on the methods, we’ll sink it near the Taiyō Maru. Then we’ll lure the enemy’s fish-shaped submarine far away from there. We’ll keep it at least thirty minutes away from the Taiyō Maru. Our submarine has a wireless device installed, so we’ll receive constant updates on their movements. During those thirty minutes, divers from this ship will go down to search through the Taiyō Maru and locate where the gold bullion lies. We can divide this into thirty-minute intervals and repeat the process as many times as needed.”

Therefore, they decided to proceed with that method regardless. After summoning the operators and giving them detailed instructions, they proceeded to submerge the submarine. At last, the battle between Akechi’s submarine and the enemy’s fish-shaped submarine was about to begin.

The Striped Phantom

At the seabed where the Taiyō Maru lay sunken, the fish-shaped submarine cruised ominously through the depths. On its back crouched the Iron Mermaid, as expected. This monster was likely issuing commands to the henchmen inside through the submarine’s upper glass window, straddling the vessel like a general astride his steed. Suddenly, the water stirred above as a large black object came swooping down. It was Akechi’s submarine. Designed for sightseeing tours, this craft had thick glass windows at the front and sides. Light from its cabin lamps leaked through these panes, giving distant observers the eerie impression of a three-eyed monster glaring from unnatural sockets.

When the Iron Mermaid noticed it, it stiffened as if startled and fixed its gaze in that direction. The submarine descended to the same depth as the fish-shaped submarine, came to a stop, and abruptly began flicking its interior lights on and off. Each time, the three glass windows would darken and brighten as if blinking. This was emitting a Morse signal using light, exactly as instructed by Detective Akechi. They were transmitting that telegraphic Morse code signal—dot-dot-dash—via light. They were testing whether anyone in the monster gang could at least understand Morse code.

Then, the two eyes of the fish-shaped submarine began to blink rapidly. This was their answer showing they understood Morse code. Therefore, our side sent the actual message. “Leave this place immediately! Withdraw at once! If you do not withdraw, we will fire torpedoes!” We didn’t have any torpedoes, but since our submarine had the same shape as a navy submarine, the enemy was sure to be alarmed when we said that.

Just as planned, the fish-shaped submarine started moving. It was moving away from the Taiyō Maru, fleeing to some unknown location.

Our submarine immediately gave chase. The two small submarines were engaged in a seabed race. The three-eyed monster pursued the two-eyed small whale—in their wake, seawater churned violently, scattering fish aside while long seaweeds thrashed wildly as if struck by a storm, creating a fearsome chase across the ocean floor. Detective Akechi’s submarine was, after all, a sightseeing vessel and lacked significant speed. Unfortunately, it couldn’t match the fish-shaped submarine’s velocity. The distance between them only continued to widen steadily.

After chasing them for about five minutes, they lost sight of the enemy. The enemy submarine had turned off its two glowing eye-like headlights. Then, blending into the darkness of the seabed, it vanished somewhere out of sight. The operators felt as though the enemy had suddenly disappeared as if wiped away. It felt as though they had used ninjutsu. But in any case, since they had driven off the enemy, all that remained was to circle around the Taiyō Maru and maintain their vigilance. Therefore, they sent a wireless message to Detective Akechi on the Hayabusa Maru.

“The enemy submarine and Iron Mermaid have fled. The main force remains on alert nearby. Immediately deploy the divers.” Upon receiving this wireless message, the Hayabusa Maru promptly sent down to the Taiyō Maru a diver who had been prepared and waiting. 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’s cabin he had entered once before. Since the Iron Mermaid had fled, there was nothing to fear now. All he needed was to locate where the gold bullion lay hidden. As he swung the underwater lamp about to illuminate the area and scanned every corner of the spacious ship’s cabin, he noticed a large square hole gaping in one wall. "Oh!" he thought. Upon closer inspection—though shells covered its surface making details hard to discern—there stood a door there, and it stood open.

It couldn't have opened by itself. Someone must have come before me and opened the door. When the diver thought that far, he froze in shock. The Iron Mermaid shouldn't be here anymore. Then who had opened it? Or maybe those monster gang bastards had broken in here long ago and stolen the gold bullion? Either way, this was an emergency. To confirm his suspicions, he brandished his lamp and cautiously peered through the doorway.

Then, inside that small room, there was something glowing dimly. The underwater lamp lay on the floor of the room. Startled, he looked closer—Oh! A truly eerie, bizarre creature was squirming right there! It had the shape of a human. However, it was not an ordinary human. Thick jet-black stripes covered its entire body. It was a black-and-white striped monster. There are sea bream with beautiful stripes. It was a striped monster exactly like that.

Its face was human but resembled a gorilla's—a terrifying creature. That face glinted as if sheathed in glass, with something like a jet-black jagged crest protruding from behind its head. At the ends of its feet were large webbed appendages like a seal's flippers. The monster abruptly turned toward him, clutching a wooden box under its arm. Behind it against the wall, similar boxes sat stacked in a low pile.

"Ah, I see. The gold bullion was here. It was put into these wooden boxes and stacked here."

The diver instantly realized it. The striped monster was indeed the gold bullion thief. The diver shouted into the telephone mouthpiece inside his diving helmet: “I’ve found the gold bullion thief! It’s a striped monster! I’ll catch him! Send reinforcements immediately!” With that declaration, he suddenly lunged at the striped fiend.

Monster crab Because he was in deep water, he couldn't lunge at it abruptly. Floating lightly, as if swimming, he grappled with his opponent.

The striped monster, upon seeing that, was startled and tried to drop the gold bullion box and flee, but it was already too late. At that moment, a terrifying grapple began between a monster resembling a striped sea bream and a diver who looked like a Western-armored ghost. Although not as much as the outer room, that room too had accumulated twenty years' worth of ocean debris. As the two grappled, the debris swirled up murkily, and the surroundings became as if enveloped in smoke.

The striped monster kept trying to flee—to flee—so as the two grappled, they had unknowingly moved outside the door and reached the base of the iron staircase leading up to the deck. Around there, kelp-like seaweed with large leaves grew abundantly. Fish that had lagged behind were also swimming there. In the midst of this, the armored ghost and the striped monster tumbled sideways and upside down, locked in combat. Unlike fights on land, the grapple at the seafloor was a slow, eerily uncanny thing, like slow motion in a movie.

When they reached the base of the staircase, the striped monster suddenly gained momentum. And because it was flopping and thrashing about like a fish, the diver's gripping hand slipped free. Then, the monster kicked the water with the large webbed appendages on its feet and swiftly ascended up the staircase. The diver was wearing heavy lead-weighted shoes, so he couldn't possibly imitate that. He had no choice but to climb the stairs one step at a time. Unfortunately, he finally let the enemy escape.

The diver hurriedly returned to the original cabin, grabbed the underwater lamp, and climbed up to the deck. From a spot slightly removed from the Taiyō Maru's massive hull on the seabed, he saw a white light rapidly moving away into the distance. It was an underwater lamp. Since the monster had fled without one, this couldn't be it. What on earth was it? "Ah, I see. My friend must have dived down after me. He found the monster and is chasing it now."

The diver, having thought this, hurriedly moved closer in that direction. Earlier, through the telephone in the diving helmet, he had called out to the Hayabusa Maru, "Send reinforcements," so another diver had dived down. The monster, lacking a light, lost its sense of direction and, while fumbling around in the kelp forest, found itself ambushed by two divers. The underwater lamps, like the monster’s glowing eyes, were closing in rapidly from both the right and left.

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 striped figure of the monster concealed itself behind a large rock. The two divers hurried there, but they couldn’t run as swiftly as they could on land. When they finally reached behind the rock, there was nothing there anymore. Wondering where it had gone, they swung their underwater lamps around and scanned in all directions, but there was no sign of the enemy anywhere. In just that short time, there was no way it could have escaped far. But aside from this large rock, there was nowhere else to hide. The two divers made gestures that seemed to say, "How strange!" and exchanged 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 squirmed. Startled, the two divers directed their underwater lamp toward it. But no—it wasn’t a rock. Something large—exactly like a rock yet of unknowable nature—had detached from the base and was making its way toward them. "Ah! It's a crab!"

One diver involuntarily shouted inside his helmet, and his voice blared shrilly through the Hayabusa Maru's receiver. What had appeared to be a rock was in fact a single giant crab. It was a terrifying crab twice the size of a human. It came scuttling forward on eight legs, lifting its massive one-meter-long claws and rhythmically opening and closing them. Whitish eyeballs about the size of rubber balls were protruding smoothly. It approached while swiveling its eyeballs round and round.

A scream like "Waaah!"—doubled—resounded through the Hayabusa Maru's receiver. The two divers screamed in unison. And then, they suddenly fled. The monster crab chased the fleeing divers for five or six meters but, for some reason, turned around and began moving away into the distance. And then, as if melting into the darkness, it vanished from sight.

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 to give a detailed account of the underwater events, Detective Akechi—who had been listening—tilted his head slightly and made this remark.

“There’s no way a crab that large could exist around here. It might just be a villain’s trick. They might have put on a crab costume and escaped. That costume might be made of thin metal or vinyl. And they might have folded it up small and hidden it inside a hole in the rock.”

“Huh? So does that mean the gold bullion thief was inside that crab?”

One of the divers exclaimed in surprise. “I can’t think of any other explanation,” said Detective Akechi. “For someone to hide behind a rock and vanish like that—it’s beyond human capability. The phantom gang of gold bullion thieves are magicians. They’ve finally shown their true colors. This is getting interesting. For me, there’s no challenge worth pursuing unless my opponent is like a magician.” The famous detective smiled brightly as he said this, running his fingers through his disheveled hair.

Scattering Gold Bullion

By that time, the western sky had already been dyed crimson by sunset clouds. The sun was visibly sinking. Before long, the eastern sky grew completely dark, the darkness spread westward, and night finally fell. However, if the enemy had discovered the gold bullion's location, they couldn't afford to rest just because it was night. Detective Akechi, the captain, and Mr. Miyata—Kenkichi's father—huddled together to discuss their plans. And so it was decided they would use a large contraption to haul up all the gold bullion at once, even at night.

The Hayabusa Maru had prepared a large net-like structure made of thick iron chains. It was a device for hoisting heavy cargo. They would attach wire ropes to it, lower it to the seabed with a crane, place the boxes of gold bullion into the iron chain net, and hoist it up. Once that was decided, they radioed the submarine monitoring the enemy's fish-shaped submarine to surface once. Then, after making thorough preparations, they would submerge again along with the iron net and have them maintain vigilance until the retrieval was complete.

It was decided that three divers would accompany the iron net, but since that alone wasn’t sufficient for security, they also resolved to submerge that massive iron sphere—the diving machine—along with it, stationing it outside the Taiyō Maru’s deck hatch to keep watch. While all the crew members were working together to make these preparations, Kobayashi Shōnen clung to Detective Akechi and kept pleading. “Please, Detective, let me ride in the diving machine.” “I could never manage to imitate the divers as a child, but with the diving machine, it should be all right.” “I can just ride in front of the engineer.” “There’s enough space for that.” “Please, Detective, ask them for me.”

Detective Akechi loved Kobayashi Shōnen as if he were his own child, so when pleaded with so persistently, he couldn’t bring himself to refuse. Detective Akechi forced a wry smile and consulted the engineer. Then, the engineer also smiled,

“If you want to ride that badly, you can come along. It’s a bit cramped, but someone as small as Kobayashi-kun should be able to fit. If I’m with an adorable kid like Kobayashi-kun, I’ll have fun too.”

The engineer agreed. “Kobayashi-san, are you going to ride in the diving machine?” “I want to ride too...” Kenkichi said enviously. “Your father would never allow it. You’re smaller than I am and not used to adventures yet. But first, if I try riding it and it’s safe, then you can go next time, right?” Kobayashi-kun said that and comforted the boy Kenkichi.

In about thirty minutes, all preparations were completed. First, the submarine sank and began patrolling around the Taiyō Maru. Next, the diving machine submerged. Finally, the iron net and three divers descended into the depths. Kobayashi-kun was so happy he could hardly contain himself. Perched on the engineer's lap with his body curled small, he peered intently through the front glass window. The diving machine was equipped with powerful electric lights like a train's headlights, making the night sea clearly visible.

Fish were swimming outside the window. Agar-like translucent jellyfish drifted gently. They rose smoothly upward—meaning the iron sphere of the diving machine was steadily descending. It felt exactly like riding an elevator.

“Look, that’s the Taiyō Maru. Huge, isn’t it?”

At the engineer’s words, when he looked down, a massive hull blanketed with barnacles lay sprawled below. Smoothly approaching, the diving machine came to a stop near the hatch on the Taiyō Maru's slanting deck.

In the distance, something glowing like an eyeball passed smoothly by. “What’s that? It looks like car headlights.” “That’s a submarine. It’s circling around the Taiyō Maru like that. Because the enemy's fish-shaped submarine could appear at any time.”

Before long, something strange descended smoothly from above—no, not from the air, but from higher up in the sea. The iron net and the three divers attached to it. The iron net was lowered right beside the deck hatch, and the three divers, waving their underwater lights and signaling greetings toward us, descended one after another into the hatch. After they descended, three ropes and an air hose swayed gently like long wisteria vines. But soon, one of them pulled taut—it was being hauled up from above—and a diver emerged from the hatch clutching a square wooden box. And he placed that box into the iron net. After placing it inside, he returned to the hatch.

Then another diver appeared，placed a similar box into the iron net，and returned．As this process repeated—with three divers exiting and entering through the hatch—the number of boxes inside gradually increased． There were thirty gold bullion crates in total．Since transporting them all at once proved impossible，they placed half—fifteen crates—into the iron net．A diver notified them by telephone，and they commenced hoisting．

With fifteen boxes loaded, the swollen iron net—suspended by a thick iron rope pulled taut—was hoisted up, swaying gently. The three divers stood on the slanted deck, looking up at it.

However, it was when the iron net had risen about ten meters. One of the divers was leaping up in a bizarre posture and pointing upward at the iron net with both hands.

Then, the remaining two divers also raised both hands in the same manner and began dancing like madmen.

“Hmm, this is strange.” “Hello? Please raise the diving machine about twelve meters.” “There seems to be a problem with the rope holding the iron net.” “Quickly, raise it up!”

The engineer shouted into the telephone receiver. The diving machine lurched and began rising smoothly upward. It overtook the iron net and reached the rope. “Keep hoisting the iron net and diving machine at the same speed.” After giving instructions over the telephone, he moved the front handle. The diving machine’s window turned toward the rope, and a strong beam of light illuminated the area. “Ah! A crab! The crab’s hanging onto the rope!”

Kobayashi-kun involuntarily shouted. That monster crab was twice the size of a human. The creature clung to the iron net's rope and was fumbling around with something.

“Ah! This is bad! That thing’s trying to cut the rope! It’s moving a large file like a saw!”

This time, the engineer shouted. And to the telephone receiver, “Hello? Please bring the diving machine closer to the iron net.” “There’s something trying to cut the rope!” “We’ll attack with the iron claw.”

Smoothly, the diving machine approached the rope. A giant crab was squirming right before their eyes.

“Now, the battle begins!” “Just watch.” “I’ll finish off that thing with the iron claw any moment now.”

The engineer shouted valiantly and placed his hands on the front handle. With a metallic screech, the giant iron claw attached to the side of the diving machine began to move. The crab's back was right before them. The iron claw smoothly extended toward it. However, since the diving machine itself hung suspended from above, it couldn't maneuver as intended. It stopped just short of reaching its target.

“Closer! Bring it closer! More! More!” While shouting into the telephone receiver, the engineer ground his teeth and moved the handle.

"Ah! It reached! Got 'em!" When he turned the handle with a metallic clang, the iron claw clamped down hard. It seized two of the crab's legs and tore them off with a violent yank. Yet the enemy remained unfazed. Having its artificial limbs severed meant nothing. The file's movements grew increasingly frenzied, their screeching vibrations seeming to penetrate straight into the diving machine's interior. Both iron net and diving machine were being hauled upward at maximum speed.

They intended to haul it up before the rope broke. It was now about ten meters from the Hayabusa Maru. It was now or never.

But, oh—that moment arrived. Finally, the rope snapped. The monster crab detached from the rope and smoothly vanished into the distance. The iron net plummeted downward with terrifying force. The net spread out, and fifteen boxes scattered and fell in disarray. Some collided with the Taiyō Maru’s deck, others struck seabed rocks, the rotten wooden boxes shattered and burst apart, sending glittering gold bullion scattering in every direction.

Kenkichi Boy's Peril

When they realized this, the Hayabusa Maru erupted into chaos. They immediately decided to send five divers down to collect the gold bullion, but preparing to submerge five divers required various preparations. Moreover, since it was a pitch-black night, the work became all the more difficult. On the deck of the Hayabusa Maru, several bright electric lights hung down, and beneath them, a large number of crew members were dashing left and right, preparing for the dive.

Kenkichi Boy was watching the valiant scene beside his father when, having some business in his cabin, he headed toward the hatch leading down there—and noticed a sailor frantically gesturing from the dark deck across the way. Inside the ship, all the prominent figures and crew members had gathered at one side of the deck and were working on lowering the divers. The electric lights were only installed in that area, leaving the other decks pitch dark. From the pitch-dark deck, a sailor was gesturing, so Kenkichi Boy thought it strange.

“What is it?”

When he asked, the sailor smiled and answered, “Mr. Kobayashi is waiting over there. I was told to call for you, young master.”

The "Mr. Kobayashi" in question was, of course, Kobayashi Shōnen—Detective Akechi's assistant. Kobayashi Shōnen had been inside the round iron diving machine submerged to the seabed, but after the diving machine was hauled up, he should have emerged from it and been resting in his own room. Why would he be calling Kenkichi-kun at this hour?

“Where is Mr. Kobayashi?” When Kenkichi boy asked again, the sailor pointed toward the stern and said, “Over there. He says there’s urgent business for you, young master.”

he answered and started walking toward the pitch-dark stern. Kenkichi Boy thought it strange, but having never imagined there could be enemies aboard the Hayabusa Maru, and since Leader Kobayashi of the Boy Detectives Club was summoning him, he couldn't disobey an order as a member—so he heedlessly followed the sailor. The stern deck was eerily pitch dark. Even when he peered through the gloom, he couldn't make out anything resembling a human figure.

“Where’s Mr. Kobayashi? There’s no one here!”

Feeling slightly frightened as he spoke thus, the sailor replied, “Look there—beyond that barrel.”

With that, he took Kenkichi Boy's hand.

When he looked, about three meters ahead sat a large object resembling a beer barrel. It was far bigger than an ordinary beer barrel. Wondering what Mr. Kobayashi might be doing behind a barrel, he found it strange and hurried closer—but when he looked beyond the barrel, there was no one there. Since the lid had been removed from the barrel, he peered inside thinking someone might be within, but it was completely empty—containing neither sake nor water.

“Ah! What are you doing…?”

Just as he tried to say this, a large hand clamped firmly over Kenkichi-kun’s mouth. Even as he struggled, another hand held his body tightly, leaving him powerless. The sailor lifted Kenkichi-kun without hesitation, shoved him into the large barrel, sealed the lid from above, then pulled nails and a hammer from his pocket and drove them in with methodical clangs. It all happened in the blink of an eye. All the ship’s crew were gathered at the diving operation site—no one noticed. Even so—who was this sailor? After stuffing Kenkichi-kun into a barrel—what on earth was he planning?

Could it be that this sailor was an agent of the Iron Mermaid’s gang of monsters? Could it be that they had boarded the Hayabusa Maru disguised as sailors when it departed Osaka? The sailor took the long rope lying there, wound it tightly around the barrel, lifted the barrel, and carried it to the stern of the ship. 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. No sooner had it lit up than it vanished, but they immediately recognized what it was. This was none other than that fearsome fish-shaped submarine. The whale-like black hull rose halfway above the surface, its protruding glass-like dome glowing with electric light. Without doubt, it had been signaling to the Hayabusa Maru's sailor.

Then, something truly terrifying occurred. The sailor gripped the rope with both hands and lowered the barrel containing Kenkichi-kun from the ship's side railing down to the sea surface. The barrel floated, swaying gently upon the surging waves.

The sailor took off his outerwear until he wore only a shirt, threaded one end of the long rope through the ship's side railing, and holding it, descended down to the sea surface himself. While treading water, he pulled in the rope fastened to the railing, wrapped it around his body, and began swimming quietly. Needless to say, he was making for the fish-shaped submarine. As the sailor swam, the barrel connected by the rope was also pulled in that direction. And before their eyes, they drew near the fish-shaped submarine.

Then, as if it had been waiting for this moment, the round glass on the back of the fish-shaped submarine snapped open upward, revealing a human face within. “Did it work?” “Yeah, the kid’s in the barrel. Tie this rope to the tail section.”

The sailor in the water answered thus, climbed onto the fish-shaped submarine, and slid through the glass hatch into its interior. Then, the man who had been inside emerged onto the submarine's back in his place, took hold of the rope's end, and ran toward the vessel's tail section. After a short while, the man returned. "I secured it tight. It's safe now." With those words, he slid into the submarine's dorsal entrance. The round glass hatch snapped shut, and the submarine quietly sank beneath the waves. All that remained was the barrel tethered by rope, bobbing aimlessly on the swells.

The Cave's Bizarre Incident

Kenkichi Boy, having been stuffed into the barrel, appeared to have lost consciousness from sheer shock for some time, but eventually came to realize that the barrel containing him was swaying violently.

I must have been thrown into the sea. And now I'm drifting along with the waves.

And he realized.

Ah, what a heart-wrenching fate this was. Since there wasn't the slightest gap in the barrel, even if he cried or screamed, there was no way anyone could hear him.

“Dad! Mom! “Kobayashiiii-san!”

Even knowing 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. Before long, he suddenly noticed that the barrel's shaking pattern had changed. Until now, it had been swaying gently as it drifted, but abruptly, it felt like it had started rushing off in one direction. It was overcoming the waves and advancing with terrifying force. The sensation reminded him of being dragged by an extraordinarily fast speedboat.

As it was pulled along, the barrel spun round and round. Kenkichi-kun’s body turned upward and sideways as it spun ceaselessly. Each time some part of him collided with the barrel’s interior, the agony proved indescribable. Kenkichi-kun thought enduring such torment made death preferable. Soon his body wasn’t just being violently shaken—his breathing grew labored. The airtight barrel’s seal prevented water ingress but worsened air quality. Oxygen dwindled until each gasp strained. Remaining confined meant certain death.

After that, he had no idea how much time had passed—he was completely disoriented. When he suddenly noticed, the barrel had stopped moving at all. The violent shaking that had been going on until now came to an abrupt stop, and his ears rang with a dull hum, leaving behind an unsettling silence. Then, the barrel moved smoothly as if being lifted, then swayed gently—but this felt different from floating on the waves.

Then came a terrifying clang near his head, followed by a rush of cold air streaming in. The barrel's lid had opened. When Kenkichi-kun breathed in that air, he thought it tasted truly delicious. He had never imagined air could feel this wonderful. Someone lifted Kenkichi-kun out of the barrel. Looking up, he saw it was the same thug sailor from before, though now wearing different clothes.

But what surprised him even more was his current location. It resembled a mountain cave. The uneven tunnel-like space had blackish rocky walls. Kenkichi-kun wondered if he'd been brought into a thieves' cavernous hideout. Escape remained impossible. Not only did the thug sailor maintain vigilant watch nearby, but exhaustion had left his body completely drained of energy. Kenkichi-kun crouched by the barrel and simply stared vacantly at his surroundings.

Just then. From beyond the cave that had become like a deep tunnel, he caught a glimpse of something strange. Since it was dim inside the cave, he couldn’t see clearly, but it was somehow a startling, terrifying thing. As he stared in that direction, startled, the figure of that strange thing emerged smoothly from around the rock corner. Kenkichi-kun let out a cry and instinctively tried to flee. Then, the sailor pressed down on Kenkichi-kun’s shoulder with terrifying force and forced him to sit there.

“Heh heh heh, we’re not going to eat you.” “Just stay still.” “They’ve got urgent business to take care of—they’re heading out now.”

The creature had now fully revealed itself and was approaching. It was that terrifying Iron Mermaid. A monster with iron scales roughly human-sized, it had sharp jagged ridges like an iron crest running from head to back, eyes glowing blue, a mouth split to the ears from which two fangs protruded menacingly. The monster crawled over 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 hands and those legs, it crawled about freely.

Kenkichi-kun pressed himself flat against the rock wall, petrified as he watched the monster, but the creature paid him no mind whatsoever, passing right before him and exiting the cave. Then, deep in the cave, there was again a sense of something moving. When he started and looked in that direction, another Iron Mermaid, identical to the one that had left earlier, was emerging ponderously from there.

No—not just one. One after another, the same monsters came crawling out in a steady stream, like a procession of Amazon River crocodiles. Kenkichi-kun became so overwhelmed that he couldn't even count them. In truth, eight Iron Mermaids passed before Kenkichi-kun and exited the cave. It was exactly like witnessing a terrifying nightmare. He had thought there was only one Iron Mermaid, but so many had been hiding inside the cave. And then, they all filed out to who-knows-where.

What on earth was going to happen? Could it be that those monsters had gone out to interfere with the Hayabusa Maru's gold bullion salvage operation? What on earth would happen if that horde of monsters started rampaging through the sea? As Kenkichi-kun—having lost even the strength to think—was staring blankly, the sailor poked his shoulder,

“Come on, we’re heading inside.” “The Leader has been waiting.”

he said something strange. "Who on earth was the Leader?"

Kenkichi-kun was led by the sailor and walked over the jagged rocks into the depths of the cave.

After proceeding through the winding cave for a while, it suddenly became bright. There, the cave widened into a room-like space enclosed by rocks. There was a magnificent carved table, upon which stood a Western-style candlestick holding three burning candles. Beside the table stood an equally large carved chair where a terrifying figure clad entirely in black sat.

He wore a black velvet hood pulled completely over his head. Only triangular openings for the eyes and mouth had been cut into the black hood, and from within those holes, eerily glowing eyes stared fixedly in this direction. On his body, he also wore something like a loose mantle made of black velvet. This must be the Leader.

“I have brought Miyata Kenkichi.” The sailor bowed reverently and said. “Hmm, well done. So you did stuff him into a barrel after all?”

The jet-black monster asked in a thick, hoarse voice. “Yes, I disguised myself as a sailor from 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 engrossed in their diving operations, and no one noticed a thing.” “Good, good. You did well. There, that settles it... Hey, Kenkichi-kun, there’s no need to be so frightened. You’re an important hostage, you see. Just stay here and keep yourself entertained. If your father agrees to my terms, I’ll return you.”

The black monster spoke in a purring voice through the triangular mouth slit 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 creepily.

“Is that what you want to know?” “You’ve got plenty of courage for a little boy.” “That is my demand—to hand over all the gold bullion from the Taiyō Maru to me.” “If he agrees to this demand, I will return you.” “Until then, you’re to stay right here.”

Ah, Kenkichi-kun had been turned into a horrifying hostage. But who—or what—was this black monster? And what of Kenkichi-kun’s fate—how would it unfold from here? And what terrifying things were those eight Iron Mermaids—which had just left the cave moments ago—about to begin?

Disappearing Fish-shaped Submarine

Aboard the Hayabusa Maru, preparations were finally completed, and five divers descended to the seabed to collect the scattered gold bullion. 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 into the water along with the divers. The five men carrying underwater lamps would locate boxes of gold bullion on the seabed and transport them into the iron net. After a full hour, they finally managed to load eight boxes into the iron net. Initially, they had placed fifteen boxes into the net, but seven broke upon impact, scattering their gold bars that became buried in the seabed sand and proved impossible to recover quickly. When they loaded eight boxes into the net, one diver used the telephone in his diving helmet to request that the Hayabusa Maru haul it up immediately.

On the deck of the Hayabusa Maru, upon hearing that phone call, they hauled up the iron net's rope with machinery at full power. This time, no giant crabs appeared like before, and the eight boxes safely reached the deck.

The five divers remaining on the seabed next scattered out and began searching for gold bars buried in the sand. It wasn’t just sand. The seabed was thick with kelp-like seaweed, making the search for gold bullion sunken within it excruciatingly laborious. However, the five men became so absorbed in trying to recover as many as possible that they wandered through the pitch-black seabed.

No matter how bright the underwater lamps were, they only illuminated three to four meters, making it exactly like walking through ink. Not even the figures of their fellow divers were visible at all. The dim underwater lamps drifted about here and there, but human shapes remained indistinguishable. They suddenly noticed two round lights approaching from afar at tremendous speed. These were no underwater lamps. They emitted stronger light. In the blink of an eye, these lights closed in right before them.

“Ah! It’s the fish-shaped submarine!” One of the divers involuntarily cried out. That voice resounded through the receiver on the deck of the Hayabusa Maru. On the deck, an engineer had been holding a receiver to his ear, but upon hearing that cry, he immediately relayed it to the captain. The captain ordered the radio operator to inform their submarine of the situation. It was to drive away the enemy’s fish-shaped submarine. On the seabed, the fish-shaped submarine was approaching right before the divers. Because two glaring eyes were dimly illuminating the surroundings, the entire shape of the fish-shaped submarine became faintly discernible.

When the divers saw it, they were so terrified that their bodies went numb, leaving them unable to scream or flee. On the long back of the fish-shaped submarine, eerie monsters were piled atop one another and clinging. That was eight Iron Mermaids. There, swarming together in a clustered mass, were those terrifying monsters—all identical in form.

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

“Waaah! Pull us up! The Iron Mermaid is here! Hurry—hurry!” The five divers all shouted in unison. Their voices boomed through the Hayabusa Maru’s receiver. The engineer hurriedly signaled the machinery crew to haul them up. With a clattering sound, the rope began winding upward.

Before long, the five divers scrambled up onto the ship's side in disarray. After having their helmets removed, they gave a detailed report of the terrifying scene on the seabed.

Meanwhile, the allied submarine, having received a wireless command from the Hayabusa Maru, immediately rushed to where the divers were submerged. When they arrived, it was just as eight Iron Mermaids had landed on the seabed. The enemy's fish-shaped submarine, having already detected our submarine, abruptly began fleeing. The monstrous fish with two glaring eyes and the three-eyed submarine pursuing it—both raced across the seabed at full speed. The small fish and other seabed creatures panicked at this sudden assault by gigantic monsters, scattering in all directions. Their frantic movements were illuminated by the two submarines' headlights, flickering gold and silver in beautiful flashes.

The two submarines were about fifty meters apart. The fleeing fish-shaped submarine raced straight toward the cape's coast, but just as it seemed about to reach the shoreline, its form abruptly vanished from sight. Assuming they had turned off their two eye-like headlights, they used their own headlights to thoroughly search the entire area. Yet that large fish-shaped submarine was nowhere to be seen—no shadow, no form. It had vanished without a trace, as though it had melted into the seawater.

The seabed in that area was covered with uneven rocks, among which were large boulders resembling small hills. They spent a long time circling around, searching whether the enemy might be hiding behind those rocks, but it was nowhere to be found.

A fish-shaped submarine that large couldn’t possibly hide so effectively. They could only think it had vanished like a ghost.

Having no other choice, they radioed the Hayabusa Maru about the situation, and the allied submarine decided to withdraw from the area.

Even so, what on earth had happened to the fish-shaped submarine? Something that large couldn't possibly have burrowed into the seabed sand. The kelp forests weren't extensive enough to conceal it either. They surfaced to check if it had risen to sea level, but no shadow or form remained - it had vanished completely.

It was the sorcery of the seabed. Had the Iron Mermaid monster group mastered some strange sorcery?

Detective Akechi's Disguise

The radio room of the Hayabusa Maru had received word from their allied submarine that the fish-shaped submarine had vanished, but before they could process this shock, a strange radio transmission began coming in from somewhere. After repeatedly calling out "Hayabusa Maru, Hayabusa Maru," it proceeded to transmit the same message over and over again. "We are holding Mr. Miyata Kenkichi. Hand over all gold bullion from the Taiyō Maru in exchange for Kenkichi-kun." "If you do not comply, we will consider Kenkichi-kun's life forfeit and dispose of him."

The radio operator, clutching the paper on which he had transcribed it, rushed to where the captain was on the deck.

"What? You're saying you're holding Kenkichi-kun?" “Mr. Miyata, where is Kenkichi-kun?” “We received a strange radio message!”

Mr. Miyata and Detective Akechi took the paper from the captain's hand and read the terrifying message. "Kenkichi said he was going to his cabin and had gone down earlier," Mr. Miyata murmured ashen-faced, "but he hasn't returned."

Mr. Miyata turned deathly pale and muttered.

“Then let’s go check the cabin.” With that, Akechi suddenly dashed toward the hatch leading down to the cabin. Mr. Miyata ran 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, Kenkichi-kun has disappeared. Please divide into groups and search the entire ship.” Detective Akechi shouted. Then a great commotion erupted as the sailors split into several groups and searched every corner of the ship, but the boy was nowhere to be found.

“This is strange.” “Sailor Kitagawa has also disappeared.” “What if he’s…”

A sailor reported. "That's it. "He might have been an enemy plant." “There’s no way Kenkichi-kun would vanish from the ship alone.” The Captain shouted frustratedly.

"He might have been taken into the fish-shaped submarine. Since all of us were gathered here focused on the diving operations, even if a submarine had surfaced on the opposite side and taken Kenkichi-kun aboard, no one would have noticed." When the engineer voiced his theory, the others thought that was likely. "However, if we don't reply to their radio message, Kenkichi might face some terrible fate. But we can't just hand over the gold bullion, Detective Akechi. What should we do?"

Mr. Miyata, with a pale face, consulted Detective Akechi. “We’ll send a radio message asking them to wait for our reply until tomorrow.” “In the meantime, there’s something I want to try out.” “With some luck, I might be able to successfully retrieve Kenkichi-kun.” Akechi said this with an air of confidence.

Thereupon, the Captain summoned the engineer and had him send a radio message requesting they wait for a reply until tomorrow.

“Detective Akechi, what exactly is this thing you mentioned wanting to try?”

When the Captain asked, Akechi voiced something completely unexpected.

“I plan to go ashore quietly tonight. Because using a boat carries the risk of alerting the enemy, we should still approach the coast in the submarine and then swim the remaining distance to shore. I’ll take Kobayashi with me. I intend to return before noon tomorrow, but it might take longer. Please delay sending the radio response until I return.” No matter how much everyone pressed him, Akechi would say nothing more. However, both Mr. Miyata and the Captain were well aware of the great detective’s capabilities, so they did not press him further and approved Akechi’s landing.

Upon hearing this, Young Kobayashi was overjoyed. When I thought about going on an adventure in the submarine with the Detective, just the two of us, I could hardly contain my joy.

Then, the two departed well past midnight. They lowered a boat from the Hayabusa Maru and transferred to the submarine floating nearby. The submarine immediately submerged and set off, reaching the coast in under ten minutes, but as that area was a desolate shore covered in rocks with no pier, they couldn’t dock alongside. It surfaced about a hundred meters away from the shore.

Detective Akechi and Young Kobayashi removed both their outer clothes and shirts, rolled them up tightly along with their shoes, tied the bundle atop their heads, and dove into the sea. The area featured sheer cliffs of towering rock where violent waves crashed against their base, whipping the water into a frothing white frenzy. Amidst these encircling cliffs lay one spot where the rocks flattened out - a place where small fishing boats would dock. The two began swimming toward this landing area with powerful strokes.

Detective Akechi, of course, and Young Kobayashi were both skilled swimmers, so they powered through the rough waves, swam vigorously across, and clambered up onto the rocky shore. Then, after drying off and putting their clothes back on there, they climbed up the gradually sloping rocks and hurried through the pitch-dark wasteland toward the nearby fishing village. The area was a barren wasteland with neither rice fields nor vegetable fields—just a truly desolate hamlet where five or six fishermen's houses huddled together. All five or six houses stood sound asleep, pitch-dark and utterly silent.

The two roused one of the houses, offered a considerable amount of money to borrow fisherman’s clothes, removed what they were wearing, and changed into them. In other words, they disguised themselves as a fisherman and his son. Their attire consisted of dirty khaki-colored pants, a torn and patched shirt, and headbands tied around their foreheads.

“Hmm, our faces are too pale.” “We should probably apply a bit of ‘makeup’.” Akechi said this, took soot that had accumulated on the fisherman’s house wall onto his hand, and smeared it thickly on his own face and Young Kobayashi’s face. Now, the two looked every bit like proper fishermen. Then, they sat down there and inquired in detail about the geographical features of the area. For this adventure, they still needed to thoroughly understand the lay of the land.

As they continued talking, the eastern sky began to brighten with a hazy glow. It was the faint light before sunrise.

Thereupon, the two expressed their gratitude to the fisherman and went outside. It was no longer so dark that they couldn’t see their footing, and no matter how much they walked, there was no danger. The two began trudging along the coast. They didn’t walk straight ahead. Instead, if there was a pine grove, they would search through it; if there was a tall hill, they would investigate its surroundings; and if there was a hole in the ground, they would peer inside—all while wandering about in search of something.

When they looked out to sea, the hull of the Hayabusa Maru appeared faintly black against the horizon. As the Hayabusa Maru reached its closest visible position, Detective Akechi had been scrutinizing the surrounding ground with heightened vigilance when he abruptly halted and fixed his gaze on a pine grove ahead. Five or six large pine trees grew there, their bases crowded with low-growing shrubs that formed a dense undergrowth. Within that thicket, the great detective spotted something.

“Be quiet. Don’t make a sound.” After whispering softly to Young Kobayashi, he approached the spot, hid his body behind the thick trunk of a pine tree, and peered through the thicket ahead. It was still dim before dawn, but as they kept staring, their eyes gradually adjusted and the area around them came into clear view. “Oh? Could there be a mole here?” Young Kobayashi stared at the spot in surprise. The grass in the thicket was quivering violently. Detective Akechi, sharp as a hunting dog, had likely noticed it some time ago.

The grass began moving even more violently. A sixty-centimeter square patch of ground started rising with a groaning creak, lifting the grass along with it. Then in an instant, the grassy soil shifted sideways, exposing a pitch-black square hole behind it.

Then, something truly strange happened. From that square hole, something smoothly stuck out its head, lo and behold! It was not a mole, but a human head. The man’s head cautiously scanned the surroundings with darting eyes; having failed to notice either observer and likely assuming nobody was present, he emerged fully from the hole. The man was dressed like a fisherman from the area. He was a robust-looking man of thirty-five or thirty-six.

What in the world was happening? From within the coastal ground, a human being had emerged. Could this man be living underground like a ground spider? What might lie beneath that black hole? Could that space have been hollowed out like an air-raid shelter, perhaps even serving as a human dwelling?

The suspicious man who had emerged from the hole returned the grass-covered soil to its original place and closed the lid of the hole. Then, after carefully surveying his surroundings once more, he began walking hurriedly toward his destination.

When Detective Akechi saw this, he poked Young Kobayashi's arm and gave a signal. Then, to avoid being noticed by him, they quietly began tailing the man. The suspicious man walked steadily away from the coast. In that direction, unlike the previous small settlement, there lay a much larger fishing village.

A tall hill towered over that path. The man was trudging along the base of the hill. At that moment, Detective Akechi once again poked Young Kobayashi’s arm. And then, he suddenly broke into a sprint. The speed was terrifying. It was as if a black wind blew past. Young Kobayashi also immediately gave chase, running with all his might. Akechi’s black shadow suddenly leaped at the suspicious man from behind. And in the blink of an eye, the man was pinned down right there.

The Naked Warriors

Why had Detective Akechi captured that man? Where did he take that man, and what did he do? We'll leave those questions aside for now as our story shifts to events occurring around noon that day, five or six hours later.

On the Hayabusa Maru anchored offshore, Miyata-san, the captain, the salvage company's engineer, and many other crew members were on deck staring at the sea surface. This was because a small boat was approaching the Hayabusa Maru from the direction of the shore. On that boat were an adult, a child, and two fishermen. The adult was rowing.

Soon, the small boat reached right beneath the Hayabusa Maru. Then, waving his hand toward the people on the deck, he shouted loudly. "Lower the ladder!" An unfamiliar fisherman was requesting to be let aboard the Hayabusa Maru.

“Who are you…?” “What business do you have…?” Someone called out loudly from the deck. “I’m Akechi.” “Take a good look at my face.” “The one here is Kobayashi…” The people on the deck were shocked to hear it was Detective Akechi. However, upon closer inspection—though his face was blackened and dirty—they realized it was undoubtedly Akechi, so they hurriedly lowered the ladder.

Disguised as fishermen, Akechi and Kobayashi climbed the ladder onto the deck and entered the lower cabin together with Mr. Miyata, the captain, the engineer, and others. After discussing something for about thirty minutes, Detective Akechi emerged onto the deck carrying a large black cloth bundle under his arm once it concluded. Then, together with Young Kobayashi, they boarded the original small boat once more and headed straight for the rocky coast.

When the two left, the Hayabusa Maru suddenly grew noisy inside. The captain gathered the crew members and sailors and issued a command. Then the crew members and sailors began bustling about everywhere, starting preparations. It was a commotion as if war had broken out. The radio operator recalled their submarine via wireless, and soon that small submarine surfaced right beside the Hayabusa Maru. Then the Hayabusa Maru's boat was lowered, and thirteen naked crew members and sailors boarded it. They wore nothing but underpants. They were all powerfully built men with rippling shoulder muscles and large biceps bulging on their arms.

All of these naked men carried oxygen tanks on their backs, held diving goggles, wore large fins on their feet, and carried strangely-shaped underwater rifles in their hands. The boat was connected to the submarine's stern with a rope, and soon afterward, the submarine departed for an unknown destination while remaining surfaced on the sea, towing the boat behind it.

About twenty minutes later, the submarine sank to the rocky seabed near the cape, its three headlights glaring brightly. In the cliff-like rock formation ahead, there was a large hollow. Last night, it was around here that the enemy’s fish-shaped submarine had suddenly vanished. At that time, the hollow had been obscured by the towering rock formation in front of it, making it impossible to see.

Earlier, Detective Akechi had left instructions that there must be a hollow near where the enemy's fish-shaped submarine had disappeared, so the allied submarine scoured the area and finally located it. The hollow was barely large enough for the fish-shaped submarine to enter. The interior lay pitch-dark and invisible, though it seemed to form an extraordinarily deep cave. The thirteen naked warriors who had been towed by the allied submarine in their boat plunged into the sea from the vessel and swam circles around the cave entrance.

The Iron Mermaids that had appeared near the Hayabusa Maru’s shore last night must have collected the gold bars scattered around that area and returned to this hollow. Those iron mermaids might emerge again at any moment. If they emerged, the naked warriors were lying in wait, intending to shoot them with their underwater rifles. The sight of thirteen naked warriors wearing diving goggles, carrying oxygen tanks on their backs, donning large fins on their feet, and gripping underwater rifles as they swam vigorously in every direction—above, below, left, and right—around the hollow was truly a gallant spectacle. Some were diving into the cave, attempting to investigate its interior.

Due to Detective Akechi's report confirming that Kenkichi had been taken into this cave, they were now attempting to swim deep into its recesses to find the boy.

Even so, what kind of terrible ordeal was Kenkichi-kun suffering through in the cave at the hands of the monster gang?

Cave Prison

At that time, the boy Kenkichi was confined in a prison cell within the cave. The hollow where the naked warriors were swimming widened as one progressed deeper, there lay concealed the enemy's fish-shaped submarine. Proceeding even further inward, the passage gradually sloped upward until it rose above sea level, becoming a waterless cavern. And there were labyrinthine escape routes like those in a stalactite cave, with room-like spacious areas here and there. The Iron Mermaid monster gang had discovered this unknown cave and made it their stronghold.

In one of the winding branching paths, there was a depression about the size of two tatami mats resembling a room, and before it stood something like a prison cell frame constructed from crisscrossed cedar logs. It was a prison within the cave.

In the pitch-black prison cell, a boy in a student uniform crouched dejectedly. That was Kenkichi. They properly brought him food, and he wasn’t being mistreated in any particular way, but since he was confined within the cell, he couldn’t go anywhere. With no one to talk to and nothing visible in the pitch-black darkness, there was nothing to do but remain still. It was truly a lonely and desolate existence.

"I wonder what Mr. Kobayashi and Detective Akechi are doing right now..." "No one must know I was brought here." "Even the great Detective Akechi probably wouldn't notice." "Oh... I miss Dad so much." "Why did I ever board the Hayabusa Maru?" "I shouldn't have done it." "If I hadn't... I could be home in Tokyo with Mom right now." As these thoughts flooded him, Kenkichi-kun suddenly wanted to shout "Dad... Mom...!" at the top of his lungs. Hot tears welled up from both eyes, spilling down his cheeks in fat drops.

When he suddenly noticed a flickering light on the rock wall outside his cell through its bars. It seemed someone was approaching with a flashlight. He wondered if perhaps the henchmen were bringing food earlier than usual. Could he possibly be dragged from this cell and made to suffer something terrible?

When he suddenly thought that, Kenkichi-kun was so terrified he couldn't stand it. He involuntarily shrank into a corner of the hollow, trembling uncontrollably. The light reflecting off the uneven rocky walls gradually intensified until a flashlight resembling a monster's eyeball came swaying closer 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 in front of the cell bars where Kenkichi-kun was confined. Then, after sweeping its beam across the rocky prison interior, the man who had arrived there shone the light toward his own face. He was one of the thieves' henchmen who always brought him food. The man held a flashlight in his right hand and carried a large black cloth bundle—about the size of a child's body—in his left. It had an unsettling, indistinct shape that defied comprehension.

As Kenkichi-kun wondered what on earth could be inside that black cloth bundle, he grew even more terrified, his body beginning to tremble uncontrollably.

“Kenkichi-kun...”

The man called out. It was a gentle voice. Kenkichi-kun thought, "Hmm, 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 a villain, but look closely—I'm Akechi.” When he heard this, Kenkichi-kun was startled and involuntarily stood up. And then he approached the cell bars and stared at the man’s face. He was disguised exactly like one of the thugs' henchmen but upon closer inspection turned out to be Detective Akechi. From within the face smeared thinly with black emerged Detective Akechi’s familiar features gradually becoming visible through smooth revelation.

“Ah! Detective!” Kenkichi-kun clung to the cell bars and cried out involuntarily.

“You mustn’t make such loud noises. I’ve come to rescue you. Kobayashi will be coming here soon.”

Detective Akechi said this and raised his flashlight high, directing it toward the tunnel-like cave opening as he swung the beam two or three times. Seemingly in response to that signal, someone approached from the pitch-black distance, and when this figure entered the beam of Akechi’s flashlight, it turned out to be a boy dressed like a fisherman.

“Oh, what a strange child has come,” he thought, but upon closer inspection, though the child’s face was smeared black, there was something reminiscent of Kobayashi-kun about him. It was indeed Kobayashi Shōnen’s disguised form. “Ah! Mr. Kobayashi…” The boy Kenkichi could not help but cry out again. Detective Akechi took out the key he had prepared, opened the cell door, and entered with Kobayashi Shōnen.

“Kenkichi-kun, I’m glad you’re safe.”

Kobayashi Shōnen suddenly embraced Kenkichi-kun. Kenkichi-kun also clung to Kobayashi Shōnen, and just like brothers reunited after a long separation, they remained embraced, never parting for what seemed like an eternity. “Kenkichi-kun, rescuing you from here will require various tricks—it’s quite a difficult task. And if we dawdle and get spotted by the enemy, it’ll be disastrous—so we must hurry. We’ll save the detailed explanations for later—let’s get started on the trick right away. First, you will exchange clothes with Kobayashi-kun.”

Detective Akechi said this and helped them himself, quickly making the two exchange their clothes. In other words, Kobayashi-kun put on the student uniform to impersonate Kenkichi-kun, while Kenkichi-kun wore the fisherman's child's clothes that Kobayashi-kun had been wearing. When they finished changing clothes, Akechi took a wet hand towel from his pocket and wiped clean the soot from Kobayashi-kun's face, then used the now-dirty towel to smear all over Kenkichi-kun's face. Then Kobayashi-kun's previously dirty face became clean, while Kenkichi-kun—who had been clean—was swiftly transformed into a sunburned fisherman's child.

“Kenkichi-kun, you’ll escape with me through the hole leading to land, board a ship, and return to the Hayabusa Maru. I’ll also take off these clothes and put on fisherman’s attire, so everyone will think a fisherman and his child are boarding the boat and won’t suspect a thing.” Akechi said this and handed the large cloth bundle he had been holding in his left hand to Kobayashi Shōnen, who was impersonating Kenkichi-kun. “Listen. With this, you’ll handle it perfectly. I’ll be back soon, okay? Until then, use your skills to keep the enemies in check.”

“Yes, I’ll be fine. I’ll definitely handle it.” Kobayashi-kun replied energetically. Then, Detective Akechi exited the cell, changed into the fisherman’s clothes he had hidden in a nearby rock hollow, and hurried toward the small hole leading to land while winding through the rocky tunnel with Kenkichi-kun in tow. Shortly after, something strange and inexplicable occurred within the thieves’ cave.

As one of the thug's henchmen walked through the rocky tunnel holding a flashlight, he caught sight of something like a black humanoid figure moving in the distance. It appeared strangely short, almost childlike. The henchman halted with a startled grunt. "That little runt shouldn't be among our crew," he thought. "Maybe that Kenkichi brat broke out of his cell and escaped."

If that were the case, it would be terrible. The man flared up and suddenly gave chase to the black figure.

“Hey! Who’s there? Stop—don’t you dare run!” He swung his flashlight beam around as he ran, but the small figure darted through the labyrinthine caves with squirrel-like agility, weaving through the winding passages until he finally lost sight of it. “Tch—nimble bastard,” he spat. *But if that was Kenkichi, the prison cell should be empty.* “Right—I’ll check that.”

The man, thinking this, hurried toward the prison cell. Then, standing outside the cell, he shone his flashlight inside to look, but strangely enough, Kenkichi-kun was right there. In the far corner of the stone cell, he was crouching 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. That key was held by the thug’s henchman disguised as Detective Akechi and wearing that jacket. So, the man dashed toward the wide cave where everyone was gathered to search for that henchman.

As he ran through the rocky tunnel, once again a small black figure flickered into view within the darkness ahead. He hurriedly swung his flashlight toward it. The figure vanished around the corner—but not before he saw it wore a student uniform identical to Kenkichi-kun's. Its height matched perfectly. The man felt an eerie sensation, as if trapped in a dream. Kenkichi-kun had somehow duplicated—one crouched motionless in the locked cell while another dashed freely through the caves. Nothing could be stranger than this. A growing unease gripped him. Acting on impulse, he charged into the Black Hooded Leader's chamber and reported everything. The leader immediately ordered all hands to search for Jack—the keeper of the cell key.

However, even after the henchmen divided up tasks and searched through the cave for nearly thirty minutes, neither the mysterious child nor Jack could be found.

It was about thirty minutes after that futile search had ended. A henchman rushed into the Boss’s room and breathlessly reported.

“Boss! He’s here! He’s here! That Jack 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. Before the report had even finished, Jack silently appeared at the entrance to the leader’s room—the man in the jacket and khaki pants.

The Mysterious Boy

The Black Hooded Leader summoned Jack before the table and scolded him. “Jack, where have you been?” “It’s been nearly an hour since we started searching for you!” “Where in hell were you messing around all this time?” Jack, standing before the leader, grinned slyly and scratched his head. “I went to the village and got treated to a feast at a fisherman’s house—that’s why I’m late…”

“What?!” “You went to the village to play around?” “Didn’t I make it clear? ‘When you finish your business, come straight back!’” “What’ll you do if associating with fishermen exposes this hideout?” “Heeh, my apologies.” “I’ll be more careful from now on.” Jack hung his head solemnly. “You’re holding the prison cell key, aren’t you?” “Something strange happened in that cell.” “It seems Kenkichi has escaped.” “He keeps darting about inside the cave.” “But when did that child become so quick? Even when everyone chases him, they just can’t catch him.”

“However, when we went to check the prison cell and peered through its bars, Kenkichi was still crouching right there inside. It just doesn’t make any sense. Everyone’s saying Kenkichi has become two. But there’s no such nonsense. One of them must be a fake. So we tried to check on Kenkichi in the prison cell, but there was no key to open its door. Because you’re holding the key! Let’s check the prison cell right away. Surely you haven’t lost the key?”

“Heeh.” “I have it right here.” “Then I’ll accompany you to the prison cell.”

With that, Jack took the lead. The Black Hooded Leader—masked and cloaked in black—followed close behind.

The two passed through the pitch-black rock tunnel and arrived before the prison cell. Jack unlocked the prison cell door with the key, and the two entered inside. When they looked, Kenkichi was crouching in the corner of the cell, head bowed. Even when the two men entered, he didn’t move a muscle. It seemed as though he might be asleep—or perhaps even dead.

The Black Hooded Leader strode over to the crouching Kenkichi-kun, grabbed his head, and forcefully tilted his face upward—but upon catching a glimpse of that face— “Ah!” With that cry, he stumbled backward in retreat. For it was not a human face. Jack too appeared shocked at what he saw. Why were the two men so startled? Because what they saw wasn’t the face of a living person—it was a mannequin’s face. Because staring back at them was the visage of a child mannequin like those displayed in clothing store windows.

The Black Hooded Leader, realizing it was a mannequin, angrily yanked off its jacket—only to discover the body beneath was nothing but a bundle of straw. They had dressed a straw bundle in clothes and made it look like Kenkichi. “That brat Kenkichi used this dummy to trick us, but he still managed to escape after all.” “You bastard!” Suddenly, he pulled out the straw bundle and stomped it to pieces. In that instant, the doll’s head came off and rolled clatteringly away, looking exactly as though a boy had been beheaded.

Even so, who on earth had brought the mannequin’s head and the straw bundle? Moreover, what on earth was Kenkichi wearing after dressing the mannequin in clothes and escaping?

The Black Hooded Leader tilted his head with an expression of utter bewilderment.

However, dear readers, you are already well aware of this. Detective Akechi—disguised as the henchman Jack—had brought the mannequin’s head and straw bundle from the *Hayabusa Maru* into the prison cell, dressed them in Kenkichi-kun’s clothes, outfitted Kenkichi-kun himself in the fisherman’s attire Kobayashi Boy had been wearing, donned a fisherman’s outfit himself, and then taken the real Kenkichi-kun back aboard the ship to the *Hayabusa Maru*. Therefore, the child flitting in and out of view inside the cave was not Kenkichi-kun but Kobayashi Boy. Kobayashi Boy was wearing Kenkichi-kun’s clothes and disguised as him.

However, the Black Hooded Leader knew nothing. Owing to the cave's darkness and Akechi's masterful disguise, he remained convinced this was the real Jack. "Right—I'll catch Kenkichi myself." "He must still be in these caves." "Jack—you're helping."

The Black Hooded Leader exited the prison cell and began circling through the pitch-black rock tunnel. Jack shone a flashlight from behind and followed. After walking some distance, they glimpsed a small black shadow darting across ahead. “Ah, there he is!” “That must be Kenkichi.” “I won’t let him escape now!” The masked leader flared 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 Black Hooded Leader accelerated even more. Since it was a child versus an adult, he couldn't win in a footrace. The gap between pursuer and pursued rapidly narrowed. Ah! This was dangerous—wasn't Kobayashi Boy, disguised as Kenkichi-kun, about to be caught any moment now?

“Ah! That guy’s climbing the stairs.” “He’s trying to escape outside the cave!” The Black Hooded Leader said frustratedly as he ran. At the top of those stone stairs was a small hole that opened onto the land above.

The Black Hooded Leader flew to the stairs, rushed up them, and tried to grab the boy's clothes from below. He was just thirty centimeters away—his hand nearly reaching him. However, the boy was quicker. He pushed aside the clump of hard, grass-covered earth blocking the surface exit and burst out of the hole in one swift motion. The masked leader thrust his head out of the hole right behind him, but upon seeing what lay beyond, gasped and jerked back inside.

Because there was something terrifying outside the hole. How and when had they arrived? Outside the hole, in the forest, five or six uniformed police officers stood lined up in a row, glaring in this direction. Kobayashi Boy, disguised as Kenkichi-kun, stood smiling, sandwiched between the police officers.

“This is bad!” “The police are here!” “Jack! We need to get out of here!” “Hurry! Get moving!”

The Black Hooded Leader rushed down the stone stairs in great haste and, pushing Jack along, dashed toward the depths of the cave. The two of them ran desperately through the winding tunnel. And the place they reached was a spacious cave near the sea. There dwelled those eight dreadful Iron Mermaids, swarming together in a clustered mass.

The Monster’s Secret

In the vast cave, eight Iron Mermaids were clustered together like caged beasts. Their dreadful iron faces bore large eyes glowing blue like phosphorus, mouths split to the ears, with fangs protruding sharply from between their lips. Their entire bodies were covered in iron scales, and from their heads to their backs ran razor-sharp, jagged edges resembling iron crests. Their torsos and tails were just like a crocodile’s, and these too were made of iron. In size, they were larger than adult humans.

Even one of them was terrifying enough, but with eight such monsters swarming together in a cluster, the sheer eeriness was beyond imagination. The Black Hooded Leader entered the monster’s den, relying on the light from Jack’s flashlight. Then, facing the Iron Mermaids, he commanded in a loud voice: “You all, listen well. Police officers will soon come storming in from the land entrance. You will go halfway and attack them. Drive every last one of them out of the hole, then block it from the inside with large stones so they can’t get back in! Understood? Now everyone—let’s head out together!”

The Iron Mermaids listened silently to their leader’s orders. For a while there was dead silence—then came a terrifying sound like countless iron pieces grating together all at once: *Clang! Clang! Clang! Clang! Clang!* The Iron Mermaids were laughing in perfect unison. "Hey! What's wrong with you all?" "Don't you recognize me?" "Why are you laughing?" "Why won't you obey my orders?!"

The Black Hooded Leader roared in a terrifying voice. However, the grating of iron showed no signs of subsiding—on the contrary, it grew increasingly violent. The Iron Mermaids kept ridiculing their leader, laughing endlessly.

“You’ve all gone mad. All right—I’ll teach you a lesson!” The Black Hooded Leader suddenly raised his booted foot and kicked one of the Iron Mermaids standing right beside him square in the face. Then, suddenly, with a terrible shift in rhythm—Clang! Clang! Clang! Clang!—the eight Iron Mermaids lunged at their leader from all directions. The phosphorus-like glow in their eyes flared up intensely, their sharp fangs gnashing with a metallic clatter as they spread clawed hands wide open, surrounding the Black Hooded Leader with ferocious expressions that seemed ready to bite at any moment.

Even the Black Hooded Leader froze stock-still upon seeing this, as though seized by horror. He couldn't fathom at all why this had occurred. Why would his subordinate mermaids suddenly rebel against their leader like this?

Then, at that moment, yet another strange thing occurred. The metallic "Clang! Clang! Clang! Clang! Clang!..." laughter of the monsters suddenly transformed into a human "Bwahahaha..." voice. The eight mermaids began to laugh like humans. It was terrifying laughter so intense it seemed to shake the cave itself. Then with a loud clattering noise, the mermaids' bellies split open, and naked humans came leaping out from inside.

“Bwahahaha... How’s that? Surprised? We’re not your subordinates. We’re eight brave warriors from Hayabusa Maru.”

From among the Iron Mermaids, the first to leap out was a young man who shouted derisively. Indeed, these were not his subordinates. All eight were complete strangers. Upon seeing this, the masked leader froze in shock, rendered speechless. “Bwahahaha... Surprised?” “These Iron Mermaids are mere toys!” “They shaped iron plates into this form and installed three oxygen tanks inside.” “That’s why they can stay underwater indefinitely without issue.” “Your lackeys crawled into these shells to frighten us.” “Their phosphorus-like eye glow comes from blue miniature lights powered by dry cell batteries.”

Detective Akechi had seen right through it. "And then he sent us—the naked warriors—to the bottom of the sea. We strapped on oxygen tanks and sneaked in through the cave entrance at the bottom of the sea. Then we scared your eight subordinates with underwater guns, made them strip off the mermaids' iron shells, and took their place. Your eight subordinates have been bound hand and foot, gagged, and left rolling around in that rock cave over there. Bwahahaha... How's that? Surprised?"

The masked leader had never once experienced such a terrible situation before. It was a terrible defeat. But there was no time for hesitation. The eight naked warriors looked ready to leap at them at any moment.

“Jack, follow me.” The Black Hooded Leader shouted this, then swiftly turned around and dashed off like an arrow. However, where on earth did he intend to flee to this time? He swirled his black mantle and dashed toward the exit leading to the seafloor. Jack followed right after him. After running for a while, the space before them suddenly opened up. There, water that had flowed in from the seabed had formed a pool-like expanse. It was a pool inside a vast cave. The entrance from the seabed lay far below the water’s surface, but since the cave continued diagonally upward, that area was already above the water level, and seawater pooled like a pond on the cave floor.

At the edge of the pool floated a jet-black object about the size of a small whale. It was the enemy’s fish-shaped submarine. On its back there was something like a transparent lump. It was an observation window made of plastic glass. Moreover, it was designed to open upward on hinges and also served as the submarine’s entry and exit point.

The Black Hooded Leader ran toward that shore, taking Jack with him.

“Now get on this,” “and escape to the bottom of the sea.” Having said this, he placed a long plank from the water’s edge onto the back of the fish-shaped submarine, walked across it to the glass observation window, opened it, and suddenly slid inside. “Jack—you get in too,” “and drive this.”

Summoned by the Black Hooded Leader, Jack crossed the plank and slid into the submarine. After firmly closing the observation window and taking his seat at the controls, he let out a shrill shout. “Ah! Leader, it’s terrible! The machinery’s completely wrecked!”

“Huh? The machinery?” The leader also rushed over and inspected it, but it appeared someone had smashed it with a hammer, making immediate repairs impossible. “There’s no choice—it’s our last escape route.” The Leader clapped his hands together and shouted. “Huh? The final escape route?” “On the other side of this lies a branching cave path only I know. We’ll escape into there.”

The two hurriedly opened the observation window and returned to the rocky shore they had left. When they looked toward the rear of the cave, eight naked warriors and police officers were shining flashlights as they hurried toward them. “Now hurry! This way!”

The Black Hooded Leader called out to Jack and broke into a run. After turning one corner, they came to a stop in a hollow of the rock. Placing their hands on a crevice in the rock there, they pulled with all their might and shifted a boulder roughly sixty centimeters wide. There behind it lay a hole just large enough for a person to squeeze through.

“Quick, get in here.” “And make sure to put the rock back exactly as it was.” “Then no one will notice.” “We’ll be saved.” The two entered the hole and, with great effort, returned the rock to its original position, sealing it shut.

The Giant and the Phantom “This hole has deep recesses with many branching paths." “It’s secure now.” “There’s absolutely no danger of being discovered.”

As he walked deeper into the rocky passage, the Black Hooded Leader declared with apparent confidence.

“But it’s strange, isn’t it? From the landside exit, the police are coming in; inside the Iron Mermaids, those enemy bastards are lurking; the fish-shaped submarine’s machinery has been wrecked without anyone noticing—what on earth is going on here?”

From behind, while following the Leader, Jack called out. “Hmm, it seems all of this is Detective Akechi’s doing." "That guy somehow found this cave." "And he must have schemed all sorts of things." “Even so, what I can’t figure out is that Kenkichi brat." "When did that quiet child become so nimble? It’s truly mysterious."

As the cave ceiling had become significantly lower, the Black Hooded Leader walked with his back bent and spoke to Jack behind him. Then Jack chuckled quietly as if finding something amusing,

“You still don’t understand why?”

said something strange. The Black Hooded Leader stopped in surprise upon hearing that voice and turned toward where Jack’s voice came from. “What did you say? So you knew all along?” “I know. That child isn’t Kenkichi.” “Huh? That’s not Kenkichi? Then who the hell is that? And where has Kenkichi gone?” “Kenkichi has returned to the offshore Hayabusa Maru.”

“Why did he return? Surely he didn’t swim there.” “He went by 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.”

When he heard that, the Black Hooded Leader firmly grabbed Jack’s arm in the darkness. “You knew that yet kept silent until now? Why didn’t you inform me?!”

“There’s a reason for this.” “I’ll explain later.” “But more importantly, it’s cramped here.” “Let’s head somewhere more spacious.”

“Yeah, if we go a bit further in, it'll get spacious again.” “Come this way.” The Black Hooded Leader declared this, took point, and advanced while hunched over. After progressing about ten meters, they emerged into an expansive cavern.

“This should do here. So if Kenkichi escaped to Hayabusa Maru, then who the hell was that kid I chased earlier?” “That’s Kobayashi—Detective Akechi Kogorou’s boy assistant.” “Huh? That was Kobayashi?”

“That’s right. Kenkichi couldn’t possibly move that nimbly, you see. In short, here’s what happened. Akechi Kogorou sneaked into the cave with Kobayashi, carrying the mannequin’s head and a bundle of straw. They dressed the straw bundle in Kenkichi’s clothes, attached the mannequin’s head, seated it in the corner of the prison cell, dressed Kenkichi in a fisherman’s child’s kimono, and took him back to Hayabusa Maru. After that, Kobayashi ran around inside the cave to make it appear as if there were two Kenkichis.”

“But wait—how did Akechi open the cell door? Since it’s not broken, he must have used a key. That key should only be in your possession. You didn’t lend it to Akechi, did you?” “That’s right. I don’t recall lending it.” “Then how did Akechi open the cell door?” “Leader, it’s a riddle—a rather interesting one. Care to solve it?”

At these mocking words, the Black Hooded Leader began to get angry.

“Hey, Jack! Are you trying to mock me?” “This isn’t the time for riddles!” “You’re still hiding something from me.” Jack continued speaking calmly.

"In other words, it's a riddle like this," he said. "There is only one key. That key was in this Jack's possession. Yet it was Akechi Kogorou who opened the prison cell door. So what's the answer to this little arithmetic problem?" In the darkness, the Black Hooded Leader fell silent. Stunned speechless, he couldn't utter a word. Soon his trembling voice emerged through the gloom.

“Then you’re….” “Hahaha… Seems you’ve caught on. The answer is that Jack and Akechi were the same person. Since we were one and the same, there was no need to borrow the key.”

The inside of the cave suddenly lit up. Jack turned on a flashlight and illuminated his own face. Within that circular light, instead of Jack, there was the face of the famously disheveled-haired Akechi Kogorou, smiling 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. "You... You really were Akechi after all."

The flashlight beam shifted to illuminate the Black Hooded Leader. The masked fiend stood with arms outstretched, frozen mid-lunge toward Akechi—a truly terrifying sight. “Finally caught on, have you? “Rather slow on the uptake for someone of your reputation. “But one mystery remains. “Where did the real Jack disappear to? “When exactly did he and I switch places? “I imagine you’re dying to know.”

I was certain there had to be an escape route to the surface within this cave. So, disguised as a local fisherman and searching along the coastal cliff, I spotted Jack emerging from that hidden hole in the woods. I followed Jack’s trail, then suddenly pounced on him from behind and subdued him. And took him to the police station in the village over there. From that time onward, arrangements had been properly coordinated with the police.

I returned once to Hayabusa Maru and had the thirteen naked warriors sneak in through the entrance of the undersea cave. The ones who defeated your subordinates inside the Iron Mermaids were those warriors. Then I disguised myself as Jack, took Kobayashi with me, entered the cave from the land side, rescued Kenkichi-kun, put him aboard a boat, and delivered him to Hayabusa Maru. And then I returned here. That’s why Jack hadn’t been seen for a while.

“Hahaha… I feel sorry for you, but your Iron Mermaid monster squad has been completely wiped out now.” The circular flashlight beam continued illuminating the masked leader. He remained utterly still and silent, like a statue carved from black stone. Akechi pressed on with his explanation. “You invented the Iron Mermaid to shock the world. You fitted thin iron armor with oxygen tanks so someone inside could survive underwater indefinitely.”

When such terrifying contraptions slowly emerged from the sea, those who witnessed them believed they were genuine monsters. Even the newspapers stirred up a commotion.

You somehow managed to uncover the secret of the Taiyō Maru's gold bullion and tried to steal the captain's will, but failed. Then Kenkichi-kun's father, Mr. Miyata, took charge of salvaging the gold bullion, and the Hayabusa Maru arrived in these offshore waters.

When you learned of this, you established your stronghold in this cave and tried to steal away the gold bullion. Thus began the underwater battle. After that, all manner of strange things occurred. We hadn't known this cave's secret, so it all felt incredibly mysterious.

But finally, I found this cave. And then, disguised as Jack, when I entered here and investigated, I completely uncovered your schemes and the secrets of the Iron Mermaid.

“And that’s why I won.” “Now then, shall we finally have you remove that mask?” “I don’t know whether there’s even a real face beneath that mask of yours.”

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 flashlight’s beam appeared one of those familiar faces—Twenty Faces, or perhaps Forty Faces. Whether this was his true face remained uncertain, but it was one they had seen during a previous case.

When told this, Twenty Faces seemed momentarily startled, but quickly regained his composure and laughed brazenly. "Ufufufu... Detective Akechi, it's been a while, hasn't it? So, what do you plan to do now?"

“It’s already decided, isn’t it? I’m turning you over to the police.”

“Heh heh heh… You’re quite full of yourself.” “Do you really think I’d obediently let you catch me?” “Like this!” As Akechi suddenly tried to grapple with Twenty Faces, the opponent slipped smoothly under his hands and abruptly fled toward the back of the cave.

The Last of the Monster Crab

Akechi swung his flashlight to illuminate the path and followed after him. But Twenty Faces moved with extraordinary speed; rounding the rock corner ahead, he vanished from sight.

When Akechi ran to that rocky corner, the tunnel split into two branches. It was unclear which way Twenty Faces had escaped. Because Akechi hesitated there for a moment, the distance between them grew even greater. With no other choice, he proceeded through one of the tunnels while illuminating it with his flashlight, but after advancing about twenty meters, he found himself at a dead end.

In great haste, he turned back and returned to the original fork in the path. Then he entered the other rock crevice. After advancing a short distance, there was something hazy squirming ahead.

It was an enormous, eerie creature. Akechi directed the flashlight's beam in that direction. Then, the hazy form came into clear view.

It was a giant crab, twice the size of a human. It glared with bulging eyes, brandished large claws, and crawled clatteringly toward the other side on eerie eight legs. It was a monster crab. Though Akechi hadn't seen it himself, this was that monster crab which had once severed the Hayabusa Maru's gold salvage ropes. There was no way such a gigantic crab could truly exist. It was a crab made of iron plates. And inside it, Twenty Faces was likely hiding.

When Akechi approached it, the monster crab would dart away, and when he stopped moving, the crab would also halt, rotating its bulging eyes and brandishing its enormous claws in a manner that seemed to say, "Stay back!" Since the monster crab scuttled sideways on eight legs, its escape was remarkably swift—even the great Akechi struggled to catch up. The cave passage became an upward slope, gradually growing steeper. Akechi chased the monster crab relentlessly.

When he darted forward to leap at it, the crab scuttled away. Its speed was such that he simply couldn’t catch up. Suddenly, he noticed that the area ahead was growing dimly bright. Hmm, that’s strange, he thought. When he looked closer, he realized the cave had an exit with outside light streaming through it. Since he had climbed quite a slope, the exit must have been located at a very high elevation.

The monster crab charged toward the exit with terrifying speed. There, a round hole had opened like a tunnel exit, and it was bright enough to be dazzling. No sooner had the monstrous crab’s hideous form loomed as a pitch-black shadow blocking the exit than it vanished in a flash through the hole to the outside.

Startled, Akechi rushed to the hole and peered outside, but the moment he looked, a wave of dizziness struck him, and he involuntarily pulled back his head. The exit was situated atop a towering cliff. Sheer cliff-like rocks continued far below where a churning sea spread out. It was tens of meters above sea level. When he cautiously poked his head out and looked, the monster crab clung to the sheer rock face with its eight legs, descending lower and lower. Since it wasn't a real crab, it couldn't grip the rock face effectively. It looked ready to slip off at any moment—just watching made one's lower back tingle with unease.

“Ah!”

Akechi let out an involuntary cry. The monster crab slid with a grating scrape. Once sliding began, there was no stopping it. The eight legs lost their grip on the rock face, and with a whoosh, the giant crab plummeted downward. Rapidly shrinking in form, it vanished into the churning sea. Even after plunging into the sea, Twenty Faces inside that giant crab likely hadn't perished. That crab had once walked unfazed across the ocean floor. There must have been an oxygen tank inside it too - allowing Twenty Faces to breathe and crawl about on the seabed.

Wouldn't he manage to escape somewhere like that? However, the cautious Detective Akechi had properly considered even such eventualities.

When he had moved the entrance rock 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 chasing the leader and Kobayashi Shōnen must have found it. And following the instructions written there, the eight naked warriors—equipped with diving masks, oxygen tanks, and flippers—swam out of the undersea cave, joined forces with five warriors who had been waiting there, and lay in wait for the enemy to appear on the seafloor.

It proceeded exactly as Akechi had planned. The Thirteen Naked Warriors were swimming vigorously around the entrance of the cave. Then, from above the sea, a large object plummeted down with tremendous force and sank swiftly to the seabed with a whoosh. It was the familiar monster crab.

When the Thirteen Naked Warriors saw this, they swarmed in from all directions and clung onto the monster crab. A fierce battle raged in the dim seabed. The monster crab brandished its enormous claws and wildly flailed its eight legs to shake off the warriors, but one creature against thirteen—even a monster crab—stood no chance. After a long and dreadful battle, the monster crab finally collapsed in exhaustion.

Like thirteen ants hauling a dead cricket, the warriors each tugged on the monster crab’s legs and rose to the sea surface.

Then, right there, their ally’s submarine opened its hatch and lay in wait. The Thirteen Naked Warriors climbed aboard the submarine, hoisted up the monster crab, and dropped it through the hatch. About an hour later, on the deck of the Hayabusa Maru, Detective Akechi, Kobayashi, and the Thirteen Naked Warriors returned. And on the deck’s floor lay the discarded shell of the monster crab, with Kaijin Nijū Mensō—Twenty Faces—gasping for breath beside it.

There, Mr. Miyata and the boy Kenkichi’s faces were also visible. Surrounding them, a crowd of sailors were raising both hands high and shouting "Banzai!" After that, it goes without saying that all of the Taiyō Maru’s gold bullion came into Mr. Miyata’s hands.