School AU!! I love writing AUs, they're probably my favorite ones to write out of fluffs, angst, etc...

When I was in Japan, I did attend school, but not high school so I don't really know what they studied so I'll just apply random math curriculum that I already studied lol...

There's a lot of time skips in this one shot so I apologize for that ;-;

(Just a little favor for you all at the end of the story, make sure you read it!)

You were a 3rd year in high school, attending school around your city. You were an average student in all the subjects except math. Math was the only subject you excelled at and all your teachers at the school insisted you should join a advanced math class, but you turned the offers down.

The last bell of the school finally rang, indicating that it was time to go home or people who participated in after school activities to go to their designated places. The teacher was erasing the sloppy writings on the blackboard as he yelled out the orders.

"Alright! If you scored a 70% or lower, I expect to see you in this class in a couple of minutes for retakes! I have a list right here, so don't you dare go sneaking out on me!" the man stood out the doorway as he passed back the test one by one. You grabbed your school bag and headed over the door as the teacher smiled down at you and handed you the paper.

"Nice work, kiddo." Kunikida complimented as you looked down to see a huge 110% across your paper.

"I got the extra credit?" you asked eagerly.

"You're the only one who got it. Here, I have something to discuss with you for a second." Kunikida walked over to his desk as you followed. He took out a couple of paper from a file and handed them to you.

"I really need you to consider taking an honor math class. You have all A's in this class and I know you'll reach even higher if you take advanced classes. This is your last year, am I correct?" he asked.

You frowned at the paper. You didn't want to take advanced classes. Not only it meant more strict teachers and more homework, there was a secret inside you that made you not go. You shook your head and smiled. "Thank you for your consideration, sensei. But I do not wish to take any advanced classes. I like the class I'm in."

Kunikida sighed. "That's what I thought you'll say..." he put his hands behind his head. "Well, I won't force you like all your other teachers are doing, but can I ask why you don't want to go?"

A small blush crept up to your face as the teacher immediately noticed.

"Ah, you have a crush in your class? Who is it?" a small smile appeared on his face.

"W-What?! N-No, that's not it!!" you blushed even more, shaking your head furiously.

The male laughed as he put the file away in his drawer. "Ok, ok. I believe you. But if you change your mind, tell me first, ok?"

"Yes, sensei. Have a good rest of your day." you bowed as Kunikida waved goodbye and you left the room. Your bestfriend was waiting for you outside the classroom, looking at you with a eager look on her face.

"So? So?? What did sensei say??" she whispered.

You sighed loudly. "He just wanted me to take an advanced math class, that's all..."

"Why don't you then? (F/N) chan, you're like really smart at math. It'll be good for you."

"I know, I know. Even my parents are nagging me about it but I just don't want to."

"Makes sense since you have a crush on Kunikida sensei~" your friend teased as you covered her mouth, your face flushed.

"S-Shut up! Don't say such things out loud!!" you scolded as the girl laughed.

"Why don't you just confess to him?"

You turned your head to the friend and gaped. "Are you serious?! Of course he's going to turn it down! No way he'll date a student! Is that even legal?!"

"Then I dunno what to tell you. This is our last year in high school, so better make it last! Gotta go take my retake for the math test! I got a fricken 67...." your friend looked at you with a bummed look.

"And that's why you should study." you said, putting your hands on your hips.

"Yeah, yeah. Whatever..." and with that, she went back in the class, leaving you alone.

The walk home was too quiet without your friend. So your mind was filled with your math teacher and the advance class all of your teachers kept bickering about.

'My last year of high school... I can't believe it's been 3 years already... It felt like just yesterday that I was a 1st year....' you pondered aimlessly, heading back to your home.

TIME SKIP

There was another bell reverberating through the school as Kunikida began his lesson in math. He stacked up the test papers and began passing back the grades down the aisle.

"I'm passing back the test you took last week. This is one of the three important math tests you'll have this whole year. It counts most of your grades so if you got a low score, most likely that'll bring you down from an A to a B-." he announced. When he finally reached to you, he handed you the paper but there was a bright pink post it note on it saying, 'Please see me after class'. You peeled off the post it note to reveal your final score which was a huge red 59%.

Your best friend who was sitting beside you looked over with a worried look on her face. "(F/N) chan, you alright?"

You just stared at the test in front of you, unable to think. Keeping your eyes on the test, you just nodded slowly. You didn't think that this would of happened to you...

Just like Kunikida ordered you, you went up to his desk after class during break time. You handed him back the test as he took it and took in a deep breath.

"(L/N). I really hate to say this to you because you're my top student but-" he waved the test. "I'm very disappointed in you."

You hung your head low as you felt tears surfacing your eyes but you blinked them away. "I'm sorry, sensei..." was all you could say.

"What's wrong? Did you not study? Did one of the curriculum stump you? If you need my help, I'll be glad to tutor you." he offered.

And then a bright idea came into your mind. Tutor. Your favorite teacher. Tutoring. You. It was perfect. "What do you mean by that?"

"Why don't we start after school? We'll start looking over this test to see your weak points and then I'll give you some worksheets regarding those subjects and we can work on them together. Sounds good?"

You couldn't help but to smile wildly. "Yes! That would be great!"

"Good, then meet me at this class after school."

"Yes! Thank you, Kunikida sensei!" you bowed so fast and since you weren't paying attention to the fact that you were so ecstatic, you banged your head onto the desk, letting out a whimper.

"(L-L/N)!! You ok?!" Kunikida stood up from his desk, looking at your with a shocked look on his face.

You smiled sheepishly as you rubbed your forehead which had a slight red mark on it. "Y-Yeah... I'm fine, I just got a little too excited..." you waved goodbye, still smiling but inside you, you were embarrassed as hell.

You showed up after school to your math teacher's class. No one was in the room except for both of you. The room was filled with empty desks, no sound, it was perfect.

"Oh hey, (L/N). I pulled out a chair for you so you don't have to sit back to your seat." Kunikida gestured towards the chair in front of his desk.

"T-Thank you..." you bowed slightly as you sat down on the chair and began pulling you supplies out from your bag.

"Alright. Now about this test. What did you think after you took it?" Kunikida took out the test and laid it down in front of you.

"I thought I did well..."

"The ones you missed most was equations. You miscalculated here and then got the wrong x." he tapped the answer that was marked wrong.

"Oh maybe because I messed up the exponents??" you pondered out loud.

"Exactly. Right here. You were supposed to multiply 10 eight times, not to 10 times 8... I thought you already knew this."

"I thought I did as well... Maybe a careless mistake?"

"Anyway, your weakness on this test was algebra, specifically equations. So I have some worksheets here that you can solve right now..." he handed you a few papers as you quickly began solving them.

"Ok, I'm done." you handed him the finished paper as he looked at you with his eyebrows raised.

"W-What? That was only a few seconds!"

"I know. Equations are easy."

He took you paper as he scanned through it with a frown. "I suggest you take this seriously and not rush it. I don't even need my answer keys because these answers are impossible to get."

"Oh..."

"(L/N). Are you trying to get bad grades to show people that you're dumb? Are you perhaps doing this for the guy you like?"

You blushed intensely. "S-Sensei! I don't have any one I like in class!"

"Well, if you do, that boy isn't worth it. You need to be yourself, that's the most beautiful part of being you and everyone else." Kunikida preached as you just blinked in surprise.

"I-I mean..." a pink dust started to form his cheeks. "Just be you and don't change who you are."

You smiled to yourself a little, feeling a bit victorious that Kunikida would say something like that to you. You felt greedy that you had those words from his all to yourself and no one to ever hear it.

'Be myself, huh....'

So as the years goes by and the graduation are getting closer and closer, you were determined to keep you math grades at top. All your other subjects were better than normal which was good. But still, your math grades were not so hot and Kunikida has been taking you to all kinds of places for tutor. A small bakery shop, a family restaurant, a coffee shop, library, those kinds of places. And truth is, you were getting sick and tired of the tutoring but you just wanted to extend your time longer with him before you graduate and go to collage and never see him again.

Your final last score on the math test was a huge 100, and Kunikida was so proud of you that he couldn't help but to give you a pat on the back and on the head.

"See? I knew you could do it. You're a smart kid, you learn very quickly."

You blushed a bit on the compliments he gave you. Although you were happy about the praise, you felt guilty. You weren't really happy with your grade, even if 100 is the highest you can get since there was no extra credit.

Graduation day finally came and you felt really nervous for some reason but at the same time, happy that you were considered an adult but sad that you had to leave your school life. The ceremony was hella long, and you didn't really pay attention to it. But after the ceremony was finally over, the students were free to walk around the school one last time. You and your best friend were walking each classroom, giving hugs and goodbyes to the teachers. The both of you finally reached to Kunikida's classroom, hoping to see him but he wasn't there. Except, there were the murmuring of your classmates, looking worried.

"Hey, what happened?" you whispered to your friend until a boy in your class answered you.

"Didn't you hear? Kunikida sensei quit being the teacher."

You felt your heart sink in your stomach and somehow felt sick. "W-What..??"

"Did you see him today at the graduation?" your friend asked, squeezing onto your hand tightly. She was worried about you.

"We all did. We got to give him flowers and such and he told us he'll be back into this room..." another girl said sadly.

"I knew that he was going to quit because I was sitting near him at the ceremony and he was talking about it with one of the other teachers!" the boy who answered you said.

"Maybe he probably left the school early. He said he had to catch the shinkansen to Yokohama." another girl spoke.

Suddenly, it hit you.

You spun around and dashed out of the class, leaving your friend behind.

"Hey! (F/N) chan!! Where are you going?!"

"Sorry! I gotta catch that train! I didn't get to thank him!!" was all you said as you rushed downstairs and grabbed your shoes from your locker, taking a single light red carnation and a letter sealed into a neat envelope.

You were getting close to the shinkansen station because you were already in the city. Your legs felt like they were about to collapse and your lungs were burning, begging for water. But you wouldn't dare to stop. Once you got closer, you saw a familiar mop of blonde hair and realized you have finally found him, waiting for the train to arrive.

You took a deep breath and shouted. "KUNIKIDA SENSEI!!!!"

The male shot his head towards you with surprise. "(L-L/N)?"

You rushed towards him as you bent down to catch your breath.

"(L/N), what are you doing here? Don't tell me you ran all the way over here!" he asked, a bit wowed by the sudden turn of events.

"M-Maybe I did... Haha..." you smiled sheepishly, your hands still on your knees. You suddenly felt a cold and wet object on your cheeks as you looked up to see that Kunikida was putting a bottle of water pressed against your cheeks.

"You must be tired running all the way here. It's a long run from the school you know."

You took the drink and ripped open the cap as you drank at least half of it. "T-Thank you..." you wiped the liquid off your lips.

"Congratulations on officially graduating from high school by the way. I never got to tell you that." he smiled.

"A-About that... I want you to have this." you handed him the light red carnation and a letter with it.

"What is this?" he asked, a little flattered by the gift.

"It's a light red carnation and a letter I wrote for you. Sorry it's only one flower..."

"I actually like getting only one flower than a hundred flowers. It feels more, special..."

You suddenly bowed again, staying in the position when you were still speaking. "Thank you so much for everything, Kunikida sensei. You meant a lot to me." you said boldly. Kunikida patted your head once more with a small but genuine smile.

"No problem, kid. I was glad to have you as my student."

You stood back up again, a small blush creeping into you cheeks. You suddenly lunged forward to give him a tight hug but pulled away again quickly.

"Thank you again so much for everything Kunikida sensei!" you declared again.

"Whatever you do, be yourself and don't change yourself for anyone, (F/N)." he gave you a warm smile as you felt tears rolling down your cheeks.

"Yes! A-And-" you felt your heart beating a mile a minute now, your cheeks burning. "I love you, Kunikida sensei!!" you were finally able to shout out those words and before Kunikida could say anything, you turned around and ran back as the teacher watched your figure slowly fading away.

Epilogue:

Inside the letter was more of an apology letter saying that all this time, you flunked your grades on purpose just so Kunikida could tutor you. You didn't think you could of done it, but once you pulled it off, you were shocked at yourself too. You told him it was a dumb choice to make, especially in your last year of high school. You thanked him many times in the letter and telling him that you had a teacher crush on him. You also told him that the light red carnation you gave him symbolizes admiration, meaning that you admired him.

And you made one promise:

That if quits the job as a teacher, you'll somehow find his new job and work as an accountant there so you can meet him again.

Now here you are, standing in the middle of a certain office called the Armed Detective Company, with your formal math teacher in the room.

The president introduced you to everyone in the company. "Meet our new assistant, (L/N) (F/N). She'll be working with us from now on."

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I felt like Kunikida's personality was a little bit too smiley on this one shot wahhh ( ͒˃̩̩⌂˂̩̩ ͒)

Anyways, I have a question for you all.

I was thinking of publishing another book and this one shot gave me an idea. (I only published one story so far and it's this one shot so it's kinda lonely in my published list;-;)

Should I write a BSD school AU?? I want to pairings to be Chuuya x Reader and maybe a slight Dazai x Reader with it.

I know it might sound a little crazy or weird about BSD having a school AU out of all AUs, but I seriously love writing AUs.

I was also thinking that since this is a school AU, I didn't want to include all the ability things so fantasy wise will be put aside.

Please let me know in the comments, I would really like your guy's feedback, thanks!! :)))