Pathway to Japanese Literature

Mysterious Letter

Allow me now to introduce you all to the boy science detective Tsukahara Toshio-kun.
Toshio-kun was twelve years old this year, but he was a clever child whom even adults could not surpass.
At six years old, he had discovered on his own that the sum of a triangle's internal angles equals two right angles, astonishing his father.
During his first year of elementary school,

"Rapeseed blossoms—children peering upside-down from the embankment"

he composed this haiku and made his schoolteacher gasp in surprise.
By his second year of elementary school, he already possessed knowledge equivalent to a middle school graduate.

Toshio-kun liked literature, but he was even more interested in science. Try asking Toshio-kun about automobile construction—he would immediately draw an ingenious diagram and explain it to you. Or try asking about the size of an elephant’s red blood cells? Just try asking him. He answered without hesitation: 9.4 microns. The model Toshio-kun created to explain planetary motion was patented and came to be used in middle schools and technical schools. For these reasons, Toshio-kun left elementary school midway and came to conduct his research through self-study.

Not long after that, Toshio-kun developed a fondness for detective novels on a whim and eventually resolved to become a science detective himself.
To become a detective, one needed knowledge of zoology, mineralogy, botany, physics, chemistry, and medicine. Toshio-kun studied diligently, and within three years, he mastered all those fields of study.

Toshio-kun's father had a small laboratory built for him next to their home in Kōjimachi Sanbanchō.
Inside, Toshio-kun peered into microscopes and fiddled with test tubes while conducting experiments late into the night in his adorable Western-style attire.
This laboratory now also serves as his detective office.

As Toshio-kun's reputation grew, he now received two or three case requests daily.
Having recently solved three major cases that had become labyrinthine, he gained renown as a famous boy detective.
However, detective work involved dealing with reckless criminals, so even Toshio-kun could not prevail through brute strength alone.

As this work involved life-threatening dangers, Toshio-kun—despite his competitive nature—had his worried parents hire a strong assistant starting that spring. The one who became that assistant was none other than myself, a third-degree judo practitioner.

Initially, Toshio-kun used to call me by my name as "Ōno-san," but lately he had taken to calling me "Big Brother." That was how close our relationship had become. I was with Toshio-kun from morning till night. When we walked around town, he would suddenly say something like, “Big Brother, you were just thinking about the Kōdōkan, weren’t you?” and surprise me. When I asked how he knew, he smiled gently and explained his chain of reasoning as if it were the simplest thing in the world.

The fact that Toshio-kun became a detective was in fact also due to his uncle from Akasaka having strongly recommended it. That Uncle had formerly been an official at the Ministry of Communications, but being an avid lover of detective novels—though he had just turned fifty—had retired and spent every day reading them, making him quite the eccentric.

Uncle was wealthy and spared no expense in buying even expensive research tools for Toshio-kun.
In Uncle’s house was a large Red Diamond passed down through generations as a family treasure, said to have been brought from Siam by Tenjiku Tokubei.
It was so famous that it had been targeted by thieves many times before, and Uncle had promised to give it to Toshio-kun as a reward if he solved this next difficult case.

Since Toshio-kun had always wanted it, he had been hoping some major case would occur.

But lo and behold!
A major incident of the highest magnitude for both Uncle and Toshio-kun had suddenly occurred—the Red Diamond had gone missing from Uncle’s house.

One day in September, a letter in a brown envelope arrived at Toshio-kun's place.
Toshio-kun always inspected a letter’s paper quality, handwriting, and postmark before opening it, but since this envelope lacked a sender’s name, he examined it with extraordinary care before finally slicing it open with a small knife and extracting its contents using tweezers.
What emerged was a half-sized sheet of blank hanshi paper.

“Big Brother, try reading this letter!”

Toshio-kun spread out the blank paper and said.
I tried to pick it up,

“Ah，don’t! Don’t touch it—I need to collect fingerprints.”

Toshio-kun said.
But since nothing was written on it，there was no way to read it even if I tried.

“Can you tell what’s written here?”

Toshio-kun asked triumphantly.

“I don’t know.”

“It’s written with alum.”

“Then you can read it by putting it in water?”

“Ah.”

Toshio-kun brought out fingerprinting tools from the shelf, applied an 8% silver nitrate solution to the edge of the paper, and set it by the window to dry in the sun.
After a while, an incomplete single fingerprint appeared black.

“Big Brother, the camera!”

When I brought the camera over, Toshio-kun swiftly photographed it, then filled a black-lacquered basin with water, spread the letter atop it, and submerged it.
Sure enough, white characters appeared.

“Toshio-kun, a major theft will occur soon, but even someone like you won’t catch this culprit.”

The message had been brush-written.

Until then, we’d received many threatening letters from criminals, but never one that announced its theft in advance. With neither location nor target specified, even Toshio-kun appeared momentarily flustered.

“This handwriting looks familiar.”

Toshio-kun said after a while.

“Big Brother, these characters were written by attaching a thread to the end of a brush’s shaft and dangling it from a high place to write.”
“Then, no matter who does it, the handwriting becomes different.”

The next two or three days passed uneventfully, but on the morning of the fourth day, Uncle from Akasaka called Toshio-kun, urging him to come immediately as an urgent matter had arisen.
Toshio-kun seemed to have a sudden realization, had me carry the bag containing detective tools, and rushed to Uncle’s house.

When we arrived at his house, Uncle—as if to say he hadn’t been waiting impatiently—ushered us into the study,

“The fact is, Toshio! Last night, the diamond was stolen!”

“What?!”

Even Toshio-kun, who never panicked, changed complexion slightly.

“Since this was a treasure for both of us, I haven’t told the police yet—but can you handle detecting alone?”

Uncle asked.

“I’ll do it alone.”

Toshio-kun declared firmly.

“Good. Then I’ll explain how it was stolen.”

With that, Uncle began his account.

The Red Diamond had always been kept in the study's safe, but when Uncle entered the study after breakfast this morning intending to read the newspaper, he found the safe door open. Startled, he checked inside but found nothing missing whatsoever.
However, when he cautiously opened the sack containing the diamond just to be sure, he was shocked to discover that instead of the gem inside, there were only meticulously folded scraps of newspaper.

“The safe has a combination lock; you can’t open it without knowing the code. Since I was the only one who knew it—and yet it was opened—I must’ve forgotten to lock it yesterday. What’s more，there were no signs of forced entry on any windows or doors，so you’d think it was someone from our household… But our family consists of me，my wife，a maid，and a manservant—all loyal servants for years—so there’s simply no basis for suspicion.”

When Uncle finished his explanation, Toshio-kun mentioned the anonymous letter that had arrived days earlier, took out a magnifying glass, and examined the safe.
Since there was a faint single fingerprint on the front of the safe, Toshio-kun applied lead white powder to clarify the fingerprint and photographed it.

When the inspection of the safe’s interior and exterior was completed, Toshio-kun meticulously examined the study’s windows, garden, and other areas, and when that was done, he returned to the study,

“Uncle, where is the diamond’s sack?”

he asked.

Uncle took out the sack from the desk drawer and handed it over.
Inside was newspaper.

“Wasn’t it you who put this in, Uncle?”

“That’s right.”

“Then are you the culprit?”

“I suppose I am.”

Toshio-kun carefully unfolded the newspaper.
It was a small piece of paper measuring about six centimeters square.
Toshio-kun held it up to the light and turned it over—

“Uncle! I’ll borrow this.”

Toshio-kun said.

“Of course. So have you identified the culprit?”

“I don’t know yet.”
“However, I’ll find it within two or three days.”

Upon returning from Uncle’s house, Toshio-kun immediately developed the photograph of the fingerprints on the safe and compared them with the photograph of the fingerprints from the letter.
The two fingerprints matched perfectly.
Then Toshio-kun handed me the aforementioned newspaper clipping and said,
“Big Brother, can you figure out what this is?”

Upon looking, it was a portion of a third-page article, and since the back side was an advertisement, I couldn’t see any particular meaning in it whatsoever.

“Hold it up to the light!”

When I held it up to the light as instructed, I saw that small holes had been poked here and there in the type with a needle.

“That’s a cipher.”

Toshio-kun said.
To the left, I will try marking dots on the characters with needle-punched holes and transcribing that newspaper article.

“Mr. Tokio Hanai of the Kondo Laboratory at the Institute of Physical and Chemical Research in Hongō Komagome Fujimae, who conducts research in full-color photographic chemistry, has succeeded in making photographic plates sensitive to colors ranging from red—previously deemed impossible—to yellow and green appear white as they should, unlike conventional photographs.
“At the same time, he has succeeded in completely eliminating ultraviolet light—which has always plagued photography, causing photographers the greatest struggle in removing it—through a unique screen……”

Cipher

“Big Brother, do you understand this cipher?”

Then, after some time had passed, Toshio-kun asked me.
I read through the newspaper clipping’s article repeatedly, but it merely stated that someone at the Institute of Physical and Chemical Research had developed a new photographic technique, having no apparent connection to this diamond disappearance case, and even when reading only the characters with needle-punched holes, they made no sense whatsoever—
“I really can’t make heads or tails of any of this.”

I answered.

“As if I’d figure it out that easily!”

Toshio-kun said with a laugh.

"So even you still don't understand, Toshio-kun?"

"I don't get it!"

Until now, Toshio-kun had detested phrases like "I don't know" or "I can't do it," never using them except when truly cornered—but finding this cipher difficult indeed, he spat out the words with a bitter expression.

Then Toshio-kun snatched the clipping from my hands and stared at it intently for about ten minutes before—

“Big Brother, please transcribe only the characters with needle-punched holes using this needle.”

Toshio-kun said.

I transcribed them as shown on the left onto a blank sheet of paper.

を行って での写真 違って今ま 能と見做さ た赤をは 黄や緑 至る迄そ く白い様に しむる事 に写真術 影者が之を とに最もお

Toshio-kun took the scrap of paper I had offered and examined it for some time,

“Big Brother, this cipher isn’t something we can solve in an hour or two.”
“Well, let’s take our time thinking it through.”

Toshio-kun said.

In the afternoon, Toshio-kun asked me to investigate which newspaper and on what date that clipping had appeared, and to bring him the paper if possible.
Hearing this, I grew deeply concerned.
Since that newspaper clipping wasn't necessarily from a Tokyo-based publication, and with no way to tell whether it came from one month ago or two months prior, I thought tracking it down would prove no easy task.

"What are you going to do with that newspaper?"

I asked.

“Just do whatever it takes!”

Toshio-kun was in a bit of a foul mood.

"But since I don't know when it was published or which newspaper it's from, there's no way I can find it in just a day or two."

I said.

“You’re such an idiot, Big Brother!”

Toshio-kun said with his cheeks puffed out in anger.

“But that’s how it is, isn’t it?”

“Big Brother, try using your head a little.”
“You should’ve realized something that obvious without me telling you.”
“Here, take this clipping and go quickly to Hongō or wherever…”

Thinking it wasn’t wise to argue when he was in a bad mood, I slipped outside as if fleeing.
But when I stopped to consider where on earth I should go, I suddenly recalled Toshio-kun’s earlier words—“Hongō or wherever”—and involuntarily slapped my thigh.
Wasn’t the newspaper clipping article about the Institute of Physical and Chemical Research in Hongō Komagome?

Admiring Toshio-kun’s cleverness, I boarded the Hongō-bound train, got off at Fujimae, went to the Institute, and visited Mr. Hanai of the Kondo Laboratory.
Then Mr. Hanai kindly met with me.

Since I couldn’t very well say it was for the cipher, I stated that I’d come to hear about the new photographic technique.

“Ah, did you see that Yomiuri Shimbun article?”

the same gentleman said with a laugh.
My heart leaped.

After listening to Mr. Hanai’s kind explanation for roughly twenty minutes, I took my leave and feigned nonchalance,
“When did the Yomiuri reporter come to visit you?”
I asked.

“Yesterday afternoon.”

If it had been yesterday afternoon, that article must have appeared in today’s newspaper.
Thinking this, when I reached the tram stop and saw a newspaper distributor across the street, I stumbled into the shop and bought a copy of the Yomiuri Shimbun.
Spreading it open, there in the third column from the bottom of page three was the exact article from the clipping.

Delighted that the newspaper search had concluded unexpectedly quickly and eager to hand it over to see Toshio-kun’s smiling face, I unfortunately encountered a blackout at Hibiya Park and arrived home around 5:30 PM as the autumn dusk deepened.

When I opened the door and entered Toshio-kun’s room, he was holding a pencil in his hand, deep in thought, unaware of my arrival.

“Well? Have you solved the cipher?”

I asked.
Toshio-kun raised his face, but his eyes remained fixed on some distant point.
Eventually snapping out of his trance, Toshio-kun,

“I still can’t solve it.”

he said bitterly.
When I looked, five or six Western books about ciphers lay open on the desk.

Just then, the telephone bell rang, so I stood up and lifted the receiver. However, Toshio-kun, who had been leaning against the desk until now, suddenly stood up as if struck by a thought,

“Yes! I’ve got it!”

he began darting around the room while shouting.

“Toshio-kun!
“The phone!”

Even when I called out, he paid no heed, until finally he clung to my waist and began acting wild.

“Toshio-kun! It’s Uncle on the phone!”
I said with a raised voice.
Upon hearing “Uncle,” Toshio-kun pressed the receiver to his ear.
Because Uncle’s voice was so loud, I could hear it clearly even as I stood nearby.

“Toshio! Have you figured out the culprit?”

“Not yet.”

“What about the cipher?”

“I just figured out the cipher’s method.”

“Just now?”

“I figured it out because of your call.”

“That’s strange!”

“Strange, isn’t it?”

“What kind of cipher is this?!”

“I’m going to solve it now.”

“I see. Give it your all.”
“Just checking on your progress.”

“I’ll do my best. Goodbye.”

How could understanding the cipher’s method have come from receiving a phone call? To me, this remained a puzzling statement.
When I moved to inquire further, Toshio-kun dashed to the bookshelf and started feverishly leafing through volumes, but moments later,

“This is troublesome... I need the book that covers this.”

he said in such a dejected manner.

“Should I go buy it?”

“No, Aoki will do.”

With these words, I pressed the call button on the desk, and after a short while, Aoki—the live-in student from the main house—entered.
Toshio-kun scribbled something on a scrap of paper and handed it to him,

“Please rush to Maruyama Bookstore on the corner and buy this book immediately.”

he instructed.

“Big Brother truly had to struggle today,” Toshio-kun declared with a grin, settling into his chair at the desk.

“After all, this is a Japanese cipher, so even if I looked through foreign books, they’d be useless. And there aren’t any Japanese books about ciphers either—I had to solve this completely on my own.”
“First, I figured these phrases—『を行って』, 『での写真』, 『違って今ま』—must each stand for single characters like ‘a’ or ‘i’.”

“Now, among these twelve groups, none had more than five characters no matter which one I examined, so I kept racking my brain wondering if there wasn’t something connected to the number five.”
“At first I thought maybe they’d converted Braille for the blind into a cipher.”
“But since Braille uses six dots, I abandoned that idea.”

“Just when Big Brother returned, I had reached the conclusion that kana must represent certain symbols as kana and kanji must represent certain symbols as kanji.”
“Then Uncle called, you see.”
“I had a sudden realization!”
“Did you figure it out, Big Brother?”

“I really don’t understand.”

“But if I mention ‘telephone,’ you’d recall immediately, wouldn’t you?”

“Huh? What about?”

“Kana are *ton* and kanji are *tsū*!”

“What’s that supposed to mean?”

I grew increasingly confused.

“This is so frustrating! It’s telegraph code!”

When I was told this, it finally clicked.
I recalled that *ton* corresponded to a dot in telegraph code—*tsū* to a dash—and that each character consisted of five or fewer combinations of these.

At that moment, the student Aoki entered carrying a small book.
When I looked, the cover was marked "Telegraph Code".

“Big Brother, set kana as *ton* and convert kanji to *tsū*, then quickly rewrite these twelve groups of characters to check which kana they correspond to!”

I finally managed to analyze them as shown on the left.

を行って ― ―― ― ― カ

での写真 ― ― ―― ―― ノ

違って今ま ―― ― ― ―― ― モ

能と見做さ ―― ― ―― ―― ― ル

た赤をは ― ―― ― ― カ

Yellow and green ―― ― ―― ワ

至る迄そ ―― ― ―― ― ニ

く白い様に ― ―― ― ―― ― ン

しむる事 ― ― ― ―― ク

に写真術 ― ―― ―― ―― ヲ

影者が之を ―― ―― ― ―― ― シ

とに最もお ― ― ―― ― ― ト

Though I went to the trouble of examining it, I couldn’t make sense of “KANOMORUKAWANINKUWOSHITO.” But when I suddenly looked up, Toshio-kun was making a face as if he’d crushed a bitter bug.

“What’s wrong?”

I asked.

Toshio-kun slammed the desk,

“They’re making fun of me!”

he shouted.

“Huh?” I exclaimed in surprise.

“Try reading it upside down!”

“TOSHIWO KUN NI WAKARU MONO KA” (“Would Toshio-kun ever figure this out?”)

Yet another of the culprit’s pranks!
After all his painstaking efforts ending up like this, it was no wonder Toshio-kun had gotten angry.

The Unexpected Culprit

I was at a loss about how to comfort Toshio-kun. At that moment, I suddenly remembered visiting the Institute of Physical and Chemical Research earlier that day. Until now, preoccupied with the cipher, I had forgotten to mention the crucial matter, and Toshio-kun also seemed unaware of it.

“Toshio-kun, I’d completely forgotten, but I actually bought and brought the newspaper that has this clipped article.”

Toshio-kun accepted the newspaper I held out with a rather unenthusiastic expression, but no sooner had he opened it than his face suddenly lit up with delight,

“Big Brother, thank you!!”

No sooner had he shouted this than, just like when he’d discovered the cipher solution earlier, he clung to my head while hopping about and flailed his legs.

“What’s gotten into you?!”

I asked, utterly bewildered.

“I’ve figured out who the culprit is!”

“Huh?”

I couldn’t help but doubt Toshio-kun’s words.

“Ah, I’m delighted!”

Having said this, Toshio-kun once again began running around the room.
I had just opened the Yomiuri Shimbun and couldn’t fathom at all how he’d identified the culprit.

“Who’s the culprit?”

“That I can’t say right now. I don’t want you asking any more questions today.”

The following morning, Toshio-kun went out saying he would mail a letter he'd written to Uncle the previous night and didn't return until around noon.
Toshio-kun had said he didn't want Big Brother accompanying him when he went out, so I remained at home. But growing somewhat worried, just as I thought to go search the area, Toshio-kun returned beaming.
And before I could ask where he had gone, Toshio-kun turned to me and declared, "The culprit who stole the Red Diamond will come here at seven tonight, so Big Brother, I need you to work with all your might to capture them."

“If we were going to capture the culprit, that would be one thing,” I thought, “but for them to come visit us seemed strange.” When I asked for the reason,

“Because they have to come!”

Toshio-kun replied coolly.

“Why?”

Silently, Toshio-kun took out a purple sack from his pocket and said,

“Big Brother, look inside this!”

He had barely opened the sack’s lid when he snapped it shut again, but inside, a crimson gem sparkled unmistakably.

“Is that the stolen diamond?”

“Is that the stolen diamond?” I asked in surprise.

“That’s right!”

“How did you get it?”

“I took it from where the culprit hid it.”
“That’s why they’ll come tonight to take it back.”

“How on earth did you investigate this?”

“I’ll tell you after we catch them tonight.”

“Could you show me that diamond?”

“No no.”

With these words，Toshio-kun gave a mischievous grin and stuffed the sack into a pocket.

I tried to figure out how Toshio-kun had identified the culprit and taken the Red Diamond from them, but I couldn't make sense of it at all.

The cipher text was merely mocking Toshio-kun as we'd seen, and yesterday's Yomiuri Shimbun also contained nothing that could serve as a clue about the culprit from what I could tell, so no matter how much I thought about it, I couldn't reach any interpretation. However, since I knew Toshio-kun's nature well, I thought it would be rude to press him with questions and resolved to follow his instructions exactly.

At 5:30 we finished dinner, and soon it became 6 o'clock.
Outside was now pitch dark, and pedestrian traffic had dwindled.
The procedure was that if the culprit came at 7 PM, Toshio-kun would open the door, and I would leap out to handcuff them.
Given my arms long trained in judo, I could handle any opponent without issue, but the thought of what sort of person the culprit might be made my heart race.

Finally, 7 PM struck.
Sure enough, footsteps echoed outside the laboratory, followed by a rhythmic knocking on the door.
Toshio-kun gave me a meaningful look and stood up to go open the door.

“Gotcha!”

With a shout, I lunged at the man who had entered.

“What do you think you’re doing? It’s me!”

The voice sounded vaguely familiar, but with his tinted glasses and face covered in a thick beard, I judged him suspicious and moved to pin him down. Yet being no ordinary opponent, he fiercely tried to throw me off, and in the next instant our struggle began with a thud and bang.

Toshio-kun also rushed toward the culprit at that moment and seemed to be doing something, but just as my strength finally prevailed and I tried to handcuff the culprit, Toshio-kun—

“Big Brother, you don’t need to do that. Uncle, please remove your tinted glasses and fake beard.”
Toshio-kun shouted.
I gasped and released my grip.
“Toshio! What on earth is the meaning of this prank?!”

With these words, the man stood up and removed his tinted glasses and fake beard—his face was unmistakably Uncle from Akasaka.

“I’m sorry, Uncle. But Uncle, you were supposed to catch the Red Diamond’s culprit, weren’t you?”

“That’s exactly it!”

Uncle said with a bitter expression as he brushed off the dust.

“Since you’re the culprit, Uncle, I was just trying to catch you. In exchange, I’ll return the Red Diamond.”

With these words, Toshio-kun took a sack from his pocket, opened the lid, and presented it to Uncle.

When Uncle saw the diamond radiating brilliant light, his face paled in astonishment.

“This is the real Red Diamond!”

With these words, Uncle took out a similar sack from his coat’s inner pocket and opened it with trembling hands.

“This is fake! When was it switched?!”

Uncle stared at Toshio-kun with a puzzled expression.

I couldn’t make sense of what was happening, so I simply stood there in a daze for a while.

“Uncle, please have a seat.
“Big Brother, please have a seat over there as well.”

With these words, Toshio-kun began triumphantly recounting the entire course of his detective work up to that point.

“Uncle, you intended to give me this diamond to test my abilities, didn’t you? When I first saw that anonymous letter, I thought the handwriting looked familiar. When I developed the fingerprints from the letter, they turned out to be yours. There was that time I collected fingerprints from Father, Mother, and you, remember? I compared them with those.”

“Then the fingerprints on the safe were also yours, Uncle. So I did consider you might be the culprit, but since someone could have stolen and used your stationery, and given that your fingerprints on the safe were only natural anyway—plus that cipher kept nagging at me—I thought it was still too early to conclusively identify you as the perpetrator.”

“But when I deciphered the cipher, phrases that mocked me appeared. Then, since the newspaper from which the cipher had been cut out was yesterday’s Yomiuri Shimbun, I obtained conclusive evidence that you were the culprit, Uncle. Since the theft was committed the previous night, an outside culprit wouldn’t have been able to cut out and insert yesterday morning’s newspaper.”

"Moreover, even if the culprit were someone from Uncle's household, you wouldn't have cut out the newspaper you read first thing. What's more, since you used to work at the Ministry of Communications and know telegraph codes inside out, I concluded you must be the culprit."

"If the culprit was you, I figured you'd staged this to test my skills. So by telling you I'd solved the case and having you come here, I reasoned you'd surely bring the diamond along."

"That's why last night I wrote to you, Uncle. When I went to mail it this morning, I swung by Ginza to buy a fake diamond and pouch. Then I tricked Big Brother into wrestling with you, and during the scuffle, I searched your pocket and swapped the real one for the counterfeit."

Uncle’s previously angry face had transformed into a beaming smile before we knew it.

“Well, I’m truly impressed. The Red Diamond is yours.”

Uncle said.

“Cutting out yesterday morning’s newspaper was my oversight.
“I’d been keeping an eye out for any science-related articles for four or five days, and when I happened upon that one, I created the cipher.
“I got so absorbed in crafting the cipher that I completely overlooked that detail and promptly called to summon you.
“Still, Ōno-kun—he put you through quite a trial, didn’t he?”

I felt like I wanted to crawl into a hole.

“I deeply apologize for that. I’m afraid I let Toshio-kun play such a mischievous trick.”

“But I did write in that letter that I’d make you suffer, Uncle.”

“Huh?”

Uncle said in surprise.

“You brought the letter, didn’t you?”

Uncle took out the letter Toshio-kun had sent that morning from his vest pocket.

“Try reading the characters formed by needle-punched holes.”

Uncle opened the letter and spent some time reading it by holding it up to the electric lamp.

“I see. I was too focused on the disguise and didn’t notice this.”

With these words, Uncle handed the letter to me.
I copied down the text on the left and, as usual, marked dots only on the characters with needle-punched holes.

Uncle, I've finally identified the culprit.
I successfully retrieved the diamond.
Please come disguised at 7 PM tonight.
Since I want to surprise Big Brother, please bring the diamond sack and this letter along with you when you come.
That cipher put me through considerable hardship.
I’ll explain all the details when we meet.
Please pardon the hasty scrawl.

From Toshio

Dear Uncle,

When you align the characters pierced with needle holes together,

“Uncle, tonight Big Brother will be made to suffer.
Please forgive me.”

“I’m no match for Toshio.”

Finally, even Uncle surrendered to Toshio-kun's intellect.

And so, the Red Diamond became Toshio-kun's rightful possession in triumphant fashion.