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Detective substitute

Summary:

Fukuzawa owes a favor for Nezu, a principal at the prestigious hero school.

And Ranpo owes Mori a favor, the man he hates with his very soul.

Simple as that.

 

Or!!
Your classic (insert character) infiltrates UA, except it’s Ranpo being a teacher there.

Notes:

There are not enough UA & Bsd crossovers.

So I took it upon myself to make a Ranpo centric one huehuehue

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

Chapter 1: 𝟏 ⌠ The substitute

Chapter Text

Fukuzawa owed a favor for Nezu, a principal at the prestigious hero high school named UA.

 

And Ranpo owed a favor for Mori, the man he hated with his guts.

 

Nezu wanted Ranpo to come to UA to identify the supposed traitor in 1-A, but not only that, he also wanted Ranpo to act as a substitute and teach the youngsters what morals are, while their actual teacher is out for a mission that needed him. 

 

As for Mori. He wanted Ranpo to get as much information as he can from the league of villains, what a stupid name… But a favor is a favor, and as much as Ranpo wants to refuse, he’s a man of his word.

 

To someone like Ranpo, the concept of heroes and villains has always sounded stupid. Not everyone needed an ability, a good reason, or an extravagant outfit to save anyone

 

 

And not everyone needed to look like a villain, or have a ‘villainous’ ability, or have an unusual taste in style, hell even a tragic story to be deemed a villain.

 

 

He never cared which side was better, he was deemed in the gray. As long as the side he’s on included his friends’ safety, you’d better bet that he’d fight on that side.

 

 

But here he is, In front of the huge gates of the famous UA. He looked so out of place with the society the world outside of Yokohama lived in.

 

 

Ranpo sighed and took out a new lollipop. He might need more energy for this. Who knew if the kids here are more unbearable than the ones back home.

 

 

Everything about the huge building said ‘government funded!,’ which was in his personal opinion, foolish.

 

 

They could’ve used a normal high school for this. Then again the most prestigious high school in Yokohama did look almost the same thing.

 

 

Key word, almost.

 

 

He walked inside, looking around the territory. Some well-taken care of plants here and there, nothing interesting. His cactus could rival any of them.

 

 

When he got in he saw a couple of hallways, and he did not memorize the map he was given. Wonderful, he just had to be stubborn and not memorize it. How he hated that even his own behavior annoyed him.

 

 

He turned his heel to walk in what seemed like a left. And turned his head to every door he passed, hoping it was the principals office. Turning once more into a new hallway as this one seemed to end, he walked.

 

 

“Hey sir! You in the brown hat!” That was when he turned his head and looked back to see a boy with blue hair. But that’s not what caught his attention, what got his attention were the engines that where attached to his legs.

 

 

He turned his glance up to look at him and not his engines. He was not going to make a bad impression on anyone today if he wanted to gain the students trust.

 

 

Even when he normally didn’t care, but Fukuzawa had offered him a lot of praises when he was done, oh and some sweets but that’s besides the point.

 

 

“May I ask what you’re doing here at UA? you don’t seem to be a student or a teacher” He asked, adjusting his glasses, “Are you perhaps lost, do you need help?”

 

 

Kunikida, found one of your descendants . He fully turned around, hands on his hips “Yes, Actually! This place is built like a maze I can’t find my way to the principals office! Can you help me?”, he answered him enthusiastically.

 

 

“Oh! The principals office? Why might I ask” Ranpo looked at him “That I can’t answer, boy”.

 

 

The student just nodded his head and gestured him to follow. When they arrived to principal Nezu’s office, Iida -the name of the student- excused himself off.

 

And as quickly he appeared, he disappeared.

 

 

Ranpo smiled at how that boy and Kunikida are almost the same, man, he was starting to already miss the agency.

 

And he only just arrived today.

 

 

He turned to the door swiftly knocking before quickly entering, not bothering to even wait for permission to enter.

 

 

The rat animal looked like he already anticipated this, “Ranpo! I didn’t expect you to be here” the principal said, “or did I?” Ranpo pouted at him “of course you did, who am I to say no to Fukuzawa’s orders” especially when they cure his never ending boredom, and the praise he gets when he’s done too.

 

 

The principal sat up as Ranpo took a seat, “care for a chess game while we discuss?”

 

“I would’ve said yes, but I need to get this over with, isn’t school going to start within a few minutes?”

 

 

Nezu hums in response and gets out a bunch of files, “I guess you’re right about that, Ranpo”, he hands him the files and Ranpo starts to look over them right there

 

 

They were student files, containing their names, quirks, parents, background. And the basic boring stuff that didn’t interest Ranpo in the slightest at all.

 

 

He would say that there was no traitor. If he were to be incompetent. Anyone could tell there was a traitor. But the problem is that every single student seemed to be suspicious, even if they’re not the traitors, they still acted weird enough for someone to say so.

 

 

But that may just be him. Because, doesn’t he just see everything basically?

 

 

Looking over at the clock, he sees that it’s almost time where classes started, and most students aren’t even here yet. Irresponsible children these days, he thinks as if he wasn’t as irresponsible— if not, worse (he still is.)

 

 

Closing the last file of the last student -Momo Yaoyorozu,- He got up and smoothed out his Inverness, giving Nezu the files back as he didn’t actually need them. “Your students sure are suspicious, all of them” he says bluntly without a care.

 

 

The intelligent rat laughs in return as he places the files back into their respectful place. Looking back at the detective who was now on his way. “Ranpo,” Said detective turns around at his name being called.

 

 

”Good luck”, At that Ranpo widens his eyes. Sharp emerald and brown eyes glancing at the principal in front of him.

 

 

He grins at him, tilting his head to the right a bit, “I appreciate your words, principal Nezu,” He turns fully to face the animal.

 

 

”but, I don’t think they call me the greatest detective for my luck” He confidently voiced, “now if you don’t need anything else from me, I’ll get going now.”

 

 

He spins around, opening the door and immediately leaving. Just right after closing the door the bell rang.

 

 

Well, guess he needs to get going now. He was about to take a turn before he froze in realization.

 

 

He didn’t know the directions here! And it was too late to ask the principal, he’s definitely busy now.

 

 

Just Ranpo’s luck, he’ll have to wander around till he find the class he’s assigned to teach.



Just a few minutes after the bell rang, students began walking off to their classrooms, some looking at the detective weirdly.

 

 

But that didn’t bother him at all, what bothered him, is that he could not for the life of him find the classroom.

 

 

Curse you Nezu for building such a complicated place! He thinks repeatedly as he goes down another hallway glancing at every class name.

 

 

When he finally found the class he was assigned to, he didn’t waste any time to get in, he was going to get this done as fast as possible if he wanted to get back home. And get rid of that stupid favor he had for stupid Mori.

 

 

As soon as he got in, the chatter inside the classroom died down and he felt eyes on him. And it made him anxious.

 

 

He looked at the students, who were looking at him like he was a mad man. He ignored them and walked to the teachers desk, with his confidence radiating off of him.

 

 

One of the students suddenly spoke up, just as he expected, “Excuse me, sir, who’re you? And where’s Mr.Aizawa?”

 

 

He looked at the student, a girl with short brown hair and rosy cheeks. Last he checked, her name was Ochako.

 

He only smiled at her, “Well, Uraraka, Your teacher won’t be here as will be unavailable for the next few weeks— or maybe months, but I don’t know the details!” He explains, only telling them the clear truth, they don’t need to know the actual details.

 

 

“So, I’m assigned to be your substitute teacher until then!” He boasted, waving his hands in clear excitement.

 

 

To be completely honest, this looks like it’s going to be fun. A little change in what he always saw; Crime, murder, cases, paperwork. A new change of scenery.

 

 

But he still is going to be fast in this, sure, this is going to be a little change. But he still wanted to do detective work, not babysit some problem children. How was he going to teach a bunch of children who believe the world is only black and white?

 

 

His morals are so much more different than these kids, and the principal expects him of all people to teach them about it!? What would he be teaching them— no. How will he teach them.

 

 

He could teach them about some random things, escalating bit by bit. Ranging from using slightly ‘unfair’ schemes to full blown manipulation.

 

 

This could go so many wrong ways. But at this point, he needs the fastest method, and right now, this one is the fastest.

 

 

The students still looked at him with wary eyes. He couldn’t blame them, these children have went through villain attacks, and the possibility of the thinking he was an undercover one was really high.

 

 

He walked back to the desk and sat down on it, not the chair, the desk was closed anyways. “Since I just got here, and didn’t really see what to do now seeing that I don’t have a schedule,” He unwraps a lollipop and popping it into his out, “we’ll be getting to know each other!” He clasps his hands.

 

 

While that was true, he didn’t have the schedule, but that doesn’t mean he doesn’t know what to do. He could’ve easily just said, ''go into your gym clothes, and meet me outside''

 

 

However, he needed to interact with the kids at least once, he has already seen how their quirks operate, moreover, he knew quirks were much weaker than abilities. But he they weren’t that weak. They just rely too much on the power they’re given that they forget how important it is to learn how to manage without them.

 

 

These kids are truly hopeless. What a bother.

 

 

“My name is Edogawa Ranpo, the greatest detective out there to exist!” He introduced himself, feeling the sense of doubt fill the room.

 

 

Of course, people always doubted him when they first met him. He always put on his childish act, knowing everything starts being boring when no one as smart as you is around. But oh how he loved seeing peoples shocked faces when he solves the mystery with only a glance.
 

 

”greatest detective? Don’t be ridiculous” He heard, a rough voice responded at his introduction. He pouted and crossed his arms, “I can hear you ya know?!”

 

 

The student, Bakugou Katsuki, only scoffed at him. “Any-ways,” He pauses and uncrosses his arms, looking at every student here.

 

 

And now starting from the back of the class, “You! Can you introduce yourself?” He picks out.

 

 

The girl, Momo Yaoyorozu, is startled by the sudden call. “Yes,” she got up and quietly cleared her throat, “My name is Momo Yaoyorozu, and I am the vice president of this class. Nice to meet you Mr. Edogawa” She introduced.

 

 

Ranpo grinned, he likes her already. She’s composed, calm, probably independent, explains why she was the Vice president after all. And from what he could tell, she was filthy rich.

 

 

But the girl soon had this face of concern, wondering if she had done anything wrong. Oh, he was disgusted, not at Momo, but at the name. “Bah! Don’t call me by my last name, it’s too stuffy! Just call me Mr. Ranpo,” He told them.

 

 

Thrown off guard once again as Ranpo pointed to the next person beside Momo. A short boy with balls for hair, weird.

 

 

”Uh! My name is Minoru Minera, Mr. Ranpo!” He firmly answered, from what he heard from other students, this boy was an expert at making the feminine students uncomfortable.



He turned his head to the next student, already getting the queue, “Izuku Midoriya!”, Ranpo was so sure this boy’s true quirk was sweating bullets.

 

 

And so on, the class had fully introduced themselves, these kids were still weary about him. Apparently, something about his childish demeanor was unsettling for them. Rude.

 

 

“Mr. Ranpo”, a student had raised his hand, wanting to ask him a question, “Yes Kirishima?” He answered, already knowing what his question was. Well, not certainly, it was either going to be a question about his ‘quirk’ or what his occupation was.




He permitted him to ask away, “what do you work as, Are you a pro hero?” The redhead had asked with curiosity, he was sure he saw Kenji in that expression the boy held.

 

Didn’t he already tell them? Bah, who cares.

“I’m the chief detective of the Armed Detective Agency,” He replied, before adding in, “As for my quirk, it’s called Ultra-deduction.” He knows it isn’t a real ability, but no one but him needed to know that.

 

The agency doesn’t know that he knows, his mafioso knew but refused to admit being defeated by an ordinary, Edgar was the same as Chuuya, just a bit more accepting towards it.

 

So they all knew that he didn’t have one, but they didn’t know that he did in fact know that. And no one needed to, it’s useless information.

 

Kirishima groaned and sat down. “Not a pro hero? Lame.” He heard him whisper to Kaminari, who chuckled quietly. He felt offended by that, being a detective is much better than being a lame hero! He wanted to say, but he kept his mouth shut, only giving an unnoticeable pout.

 

If Chuuya was here, he would’ve made fun of his pouty face. He wouldn’t leave him alone until he knew what got him this pouty.

 

Gosh, he missed his mafioso. He sighed.

 

the students were intrigued about his quirk, why was it called ‘Ultra-Deduction’? Of all things. What did it even do? Improve his thought process? Observation? Or was it just something similar to Nedzu’s High Spec and gave him a superhuman brain?

 

The answer was none of them, of course. But they all forgot that ordinary humans can be just as dangerous as quirked ones. If he had told them about how he didn’t have a quirk.

 

They’d all be looking down at him, and he hates it when people do that. But it meant that he had something to prove, and that was fun.

 

If they ever find that out, he will show them what an ordinary can do. But right now, since they don’t know what doesn’t hurt them. He’ll be nice.

 

“Any more questions?” he called out. Once again, he was met with a boy raising his hand, he smiled and permitted him to ask away.

 

Smiling dryly, this is going to be a long 9 months. He thought. He hopes that nothing holds back their teachers from completing the mission fast.

 

A long, painfully slow, 9 months.