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The Puzzle Called Class 1-D

Summary:

Class 1-D, who began the year spending all their points and earning absolutely zero back, managed to not only get this far without a single expulsion, but also beat the other classes, one of which contains one Arisu Sakayanagi, who he knows to be a genius in her own right.

If Shinichi didn’t know any better, he’d say there was someone behind the scenes, manipulating things in favor of 1-D…

Shinichi Kudo of Class 3-B has no reason to be interested in the misfits of Class 1-D.

...Not that that's ever stopped him before.

 

OR: Ayanokoji is so busted.

Notes:

For the Mouri Detective Agency 2026 Fanfic Bingo!

Prompt: School AU

(See the end of the work for more notes.)

Work Text:

“The world is not governed by opinion, but by knowledge.”

— Plato

 

 

Shinichi first heard about them through word of mouth.

 

“Seriously?! They blew through all of their points in the first month??”
“I know right? I’ve never even heard of that happening, not even with Class D!”

“My friend’s cousin is in 1-B, and she heard that they didn’t even earn a single point back!”

“Not one?!”

“That’s insane…”

 

Whispers floated through campus about this year's Class 1-D. Shinichi couldn’t exactly say he was surprised; every year, 1-D performed terribly, especially at the beginning of the year. The system was somewhat biased in his opinion, but he supposed it also depended on the teacher your class was assigned. He’d heard rumors throughout the years of Chabashira, and he could say with certainty that they wouldn’t exactly get along.

 

“I wonder how it’s even possible.”

 

Shinichi was snapped out of his thoughts by his friends’ voices. They were currently seated in a large booth in one of the campus’s more popular cafes.

 

“What, losing literally every single point?” Kaito asked, taking a bite of his chocolate cake, to which Sera nodded. “Through things like tardiness, incessant chatter, and low grades I presume,” Hakuba answered idly. “For them to lose that much though, could their entire class be like that?” Heiji asked incredulously, waving around his spoon, and causing Kazuha to quietly reprimand him.

 

“Isn’t Manabu’s younger sister in that class?” Shinichi questioned curiously, finally focusing all his thoughts back to the present. He was on pretty good terms with the Student Council President, though he’d declined joining the Council due to a wish to focus on his studies and detective work.

 

“Yeah. I’m pretty sure she got one of the highest grades of the first years, though,” Kaito commented. “I wonder why she got placed in Class D then,” Ran said, taking a sip of her drink. Kaito shrugged. “Beats me.”



ᝰ  ⚯ ˎˊ-

 

 

“The worthy administrators of justice are like a cat set to take care of a cheese, lest it should be gnawed by the mice. One bite of the cat does more damage to the cheese than twenty mice can do.”

— Voltaire

 

 

“There was a fight?!”

 

The next time Shinichi hears about them, it’s right after midterm exams.

 

“Yeah, apparently that one troublemaker, I think his name was Sudo? He got into a fight with some 1-C guys,” Heiji said. “Even Horikita was there to preside over the hearing,” Sera added. “Class C rescinded their complaint though, right?” Sonoko said conspiratorially.

 

“Eisuke said he saw Horikita’s younger sister and another boy go into the special annex yesterday when he passed by, and later he saw some of the Class C kids go in,” Ran explained.

 

“Interesting…” Shinichi said in amusement. He had just happened to be walking around during that time yesterday. He’d passed by the younger Horikita and a brown-haired boy, and come to think of it, they were heading in that direction.

 

It’s hardly one of the craziest things to happen at Advanced Nurturing High School. Still, he could deduce that Class 1-D had somehow ‘convinced’ 1-C to drop the complaints. Doing so in the empty special annex just made it even more suspicious.

 

His curiosity wasn’t exactly piqued, per se, but he was certainly gaining quite a bit of interest in the first year Class D.



ᝰ  ⚯ ˎˊ-



“Every man takes the limits of his own field of vision for the limits of the world.”

— Arthur Schopenhauer

 

 

It was the first day back in class after the third years’ first Special Test, which had consisted of a glorified murder mystery, with each class having to solve their own during a period of three days staying at one of the inns on a mountain. Class 3-B had solved it in record time, though some points were deducted for etiquette (due to a certain someone pranking the other guests).

 

Then an actual murder had occurred after the solving of the staged one, and Shinichi, Heiji, Hakuba, and Sera had definitely not competed to see who could solve it, because that would be uncouth.

 

“1-D seems to be turning things around. They got first place on the first year’s first Special Test!” Kaito exclaimed. “Class C got first on the second test right?” Aoko asked, to which Hakuba nodded. “Geez, what are A and B even doing?” Heiji shook his head faux mournfully.

 

“Hey, Ichinose is really nice,” Ran reprimanded. She’d chatted with her a few times, and they got along really well.

 

“Isn’t 1-A going through some kind of civil war?” Sera asked, arms crossed and resting behind her head. “Civil war might be a bit much…” Shinichi sweatdropped. “You get what I mean! They’ve got some kinda factions going on or something.” “One of them is led by the chairman’s daughter, Arisu,” Sonoko said, eyes closed and nodding. “Oh wow, really? You know, you’d think…”

 

Shinichi allows his friends’ voices to fade into the background as he gets lost in thought. It isn’t exactly his style to be concerned with other years, much less specific classes in other years, but it is his thing to figure out puzzles he comes across. And this, this is a puzzle worth solving.

 

Class 1-D, who began the year spending all their points and earning absolutely zero back, managed to not only get this far without a single expulsion, but also beat the other classes, one of which contains one Arisu Sakayanagi, who he knows to be a genius in her own right.

 

If Shinichi didn’t know any better, he’d say there was someone behind the scenes, manipulating things in favor of 1-D…



ᝰ  ⚯ ˎˊ-

 

 

“The unexamined life is not worth living.”

— Socrates

 

 

Apparently, he’s not the only one who thinks this. Aside from the chatter surrounding Manabu Horikita stepping down as Student Council President, and being replaced by Miyabi Nagumo, there’s also another rumor that has piqued his interest.

 

Somehow, the leader of Class 1-C, Kakeru Ryuen, has managed to broadcast the fact that he’s looking for 1-D’s mastermind, without actually broadcasting that he’s looking for 1-D’s mastermind.

 

While it’s nice to know Shinichi isn’t crazy (well, sharing an opinion with Ryuen of all people doesn’t exactly not make him crazy), it also serves to make him even more curious.

 

Somehow, he doubts the mastermind is Suzune Horikita. He’s talked with Manabu before, and from what he’s been told, Horikita the younger isn’t exactly one for cooperation. Now, that could’ve changed, what with how much the class has clearly been going through. But he’s also willing to bet that this so-called ‘mastermind’ has been working since the beginning of the year. Therefore, unless her personality happened to do a complete 180, enough so for her to be able to get along with her classmates well enough to learn things in order to subtly manipulate them, it’s unlikely to be her.

 

He could also just be reading way too much into this.



ᝰ  ⚯ ˎˊ-



“The surest way to corrupt a youth is to instruct him to hold in higher esteem those who think alike than those who think differently.”

— Friedrich Nietzsche

 

 

“Whosever group gets the highest average score at the end of the test is the winner. It’s as simple as that.”

“I see. I’d be happy to take you up on that. One thing; leave the other students out of it.”

“A good old fashioned gentlemen’s agreement, huh. Well then, it’s a promise. There’s no punishment for losing either. The only thing at stake here is our pride.”

 

Shinichi watches as Nagumo walks away, and Akane begins talking to Manabu. “I’m surprised he accepted it,” Heiji commented. “Well, he could hardly not,” Shinichi replied, sighing. “Yeah, I’m calling it. No way Nagumo is keeping that promise,” Kaito said, shaking his head. Shinichi can’t say he disagrees.





The corridor was pitch black.

 

Shinichi had woken up to both Kaito and Heiji’s snoring. Needless to say, he didn’t really feel like sticking around and struggling to fall asleep. He resolved to go and find something to drink, and maybe splash some water on his face.

 

…He’s not exactly sure how it ended up like this. 

 

“Gotta say, I was surprised to see you reaching out to me.”

 

“Do you know why I reached out to you?”

 

“Nagumo, I assume?”

 

“Correct. As it stands now, he has the second years in the palm of his hand.”

 

Shinichi was pressed against the corner that turns into the corridor. The corridor where the sinks he wanted to get to so happened to be.

 

He hadn’t meant to eavesdrop. Despite what his friends may tease him about, he doesn’t enjoy it, and he isn’t about to make it a habit, even if he’s a detective.

 

“What do you want me to do about it?”

 

“As I recall, you still owe me a favor. And you can pay that favor back by taking down Nagumo. Get Suzune on the Student Council, that would be a start. Then continue directing her behind the scenes.”

 

…Even so, this was turning out to be quite an interesting conversation. He couldn’t really see who Manabu was talking to from his current vantage point. Actually, he couldn’t see anything from his current vantage point; he only knew it was Manabu because he could recognize his voice.

 

“That’s a rather outrageous ask, don’t you think?”

 

“Indeed it is. I don’t expect you to do everything I want just because you owe me a favor. Obviously.”

 

“Well, I don’t have much information on the upperclassmen. That would be quite an obstacle.”

 

“Let me introduce you to an informant.”

 

Shinichi hears a bit of shuffling and footsteps as someone steps further into the corridor. They must’ve already been standing there, but further back, since no one turned around the corner he was watching from.

 

“Student Council Vice President and member of Class 2-B, Ikuto Kiriyama. His cover story is that he works for Nagumo, but he really serves me.”

 

“Let me be frank, Ayanokoji. I have serious doubts about your ability to pull this off. But still, I’m prepared to do exactly as Horikita orders.”

 

‘Ayanokoji…’ So that’s who Manabu was talking to. Not that he had any idea who that was, but having a name to go with the voice was nice.

 

“Nagumo’s abusing his power. He’s trying to obliterate the foundations of the school. Next year, I expect we’ll see a lot of expulsions. An unprecedented number, perhaps.”

 

“Interesting. By the way, what about your competition with Nagumo?”

 

“Oh, that will work itself out.”

 

“And how likely is it that he'll refrain from involving any third parties?” 

 

“Nagumo is unprincipled in his methods, but still, I don’t think he’d be one to break his promise. His word is good.”

 

Shinichi quickly pressed himself against the wall as Manabu and Kiriyama walked back the way they came. Luckily, they turned the opposite corner, and faded into the shadows. Shinichi was about to head back the way he came, giving up on washing his face, when heard a faint, “Manabu Horikita, you might lose this one.”

 

As the footsteps begin to fade, Shinichi chances a glance into the corridor. He’s just in time to see golden eyes and brown hair turn the corner. It was the same boy he’d seen with Horikita headed towards the special annex.

 

‘Ayanokoji…’

 

Well, at least he knows who the mastermind is now.





“I’ll expel as many people as necessary to accomplish my goals. I mean, that’s how things are supposed to be done at this school after all.”

 

All the classes watched together with bated breath as Nagumo revealed his plot to “cut off Manabu’s right hand”.

 

‘Ayanokoji…He was right. This is Manabu’s loss. Either he loses Akane, or their class loses a lot of points. He isn’t as cold as he’d like people to think though, so it’s obvious which one option he’ll choose.’ Shinichi sighed.

 

“You’re really going to spend all those points just to save Tachibana?”

 

“Please don’t do this! I brought it on myself…”

 

Manabu turned his attention to his class. “Sorry, everyone.” However, instead of frustration or any other negative emotions, there was nothing but support for his decision.

 

“You’re pretty much single-handedly demoting your entire class.”

 

“We’ll take that position again soon enough. You’ve accomplished nothing with this.”

 

“Alright, it seems everything worked out here.”

 

“Well…I guess we’ll just have to enjoy being Class 3-A for a while!” Kaito exclaimed light-heartedly, in an attempt to lift the mood as the classes dispersed. “Shopping trip, here I come!” Sonoko grinned. “Sonoko…” Ran said, in fond exasperation. Shinichi shook his head, smiling as his friends started up their usual chatter.

 

Sure, in a few months’ time, all of this would be gone. None of the things he was curious about would matter. But…as a detective, it was his job to live in the moment, and figure out the answer to any and every question that crossed his path.

 

The Mixed Training Camp had certainly been quite fruitful for Class 3-B, if nothing else. Sure, he hated to see Nagumo win. However, he’d learned the identity of Class 1-D– sorry, Class 1-C’s mastermind, and their class had even gotten a promotion out of it!

 

There will always be mysteries to solve, and he’ll always be curious about every single one. For now though, this was good enough.

 

 

“He who knows all the answers has not been asked all the questions.”

— Confucius

 

 

END.

Notes:

It was a struggle to write this ngl. I'm only moderately happy with how it turned out but it's fine. THE AO3 FANDOM FOR COTE IS SO DEPRESINGLY SMALL AND I NEEDED TO ADD TO IT SOMEHOW!!!

I added the philosophy because first i was thinking the title could be a quote, since that's how the cote episodes are named. But then I found so many I liked so I was just like "let's use ALL OF THEMMM" so now here we are.

In case you were wondering, here's a list.

Class 3-B:
Shinichi
Shiho
Ran
Sonoko
Sera
Heiji
Kazuha
Kaito
Aoko
Hakuba

Eisuke (3-C)

 

I tried to give them all at least one line, just because I took the liberty of making that list before I wrote the fic, so.

I can't remember if Classroom of the Elite had Class Presidents, but my headcanon for this fic is that Shinichi is class prez with Shiho as his vp. (I know I didn't give her any lines but I didn't know where to put herrrr) So here's this.

Shinichi: You know, the way Manabu talks about his sister, she kind of reminds me of you!
Shiho: Count your days.
Kaito: You're so dead. Bets on how long he'll live?
Heiji: 10
Sera: 10 what?
Heiji: 9
Shiho: 8

Shinichi: Would you look at the time, it seems like it's about time for another body to fall from the sky or something ahaha...
Sera: Spoiler alert, it's gonna be yours.
Shinichi: Avenge me at least?
Heiji: That's boring, there's no mystery behind it.
Shinichi: Well screw you too.

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