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A Yellow Octopus in The World of Heroes

Chapter Text

Izuku was honestly kinda shaking. They had been handed guns and knives that seemed to be useless. He had gathered with his class after the first school day had ended. Izuku, being the shy kid he was, decided not give any input when his class started talking about assassination plans.


The next day arrived in a flash, Izuku being too afraid of the consequences to tell anyone about his first day of school.


They gathered in the classroom early, waiting for their teacher. Guns lay beside their desks. It was oddly quiet for a classroom. From Izuku’s experience it was usually filled with chaos before the teacher got there.


Eventually, the students heard a slimy sound of their teacher in the hallway. Nodding to each other, they got in position.


“Ah,” The creature began. “It’s now time for role cal-“


The octopus was cut off by the class standing up. Simultaneously, they fired their guns. A barrage of bullets sprayed around the classroom as all the students tried to land a shot on their teacher.


Their teacher though, was moving at the causal speed of Mach 20. You know, as you do. By moving at such a speed he managed to dodge all the bullets with ease, all while taking roll call.


“Well, if you want to kill me you’ll have to do better than that! Now! Clean up this mess! This assassination should not affect your studies!”


Izuku’s class just sighed in defeat as they cleaned up the anti-sensei bullets. Their sensei had shown them the devastating effects said bullets and knives had on him mere moments ago. Saying something along the lines of him becoming like Tofu, the weapons slicing right through him.


“Hey! Nagisa, Midoriya!” Terasaka said. “Let’s work on an assassination plan!”




Quirk: Intimidation

When wanting to talk with someone, his intimidation overpowers his senses. This makes him snarky and somewhat aggressive.


Quirk drawbacks:

Always active so his aggression continues to show, his intelligence is also lowered. With proper training he should be able to turn it off.


Despite not wanting to go, Izuku followed him with Nagisa. He could see that he was in the same boat. Sighing, the rainbow-haired children followed Terasaka and his friends.


“So,” Terasaka began. “You’ve both been observing him, haven’t you?” 


Izuku and Nagisa looked at each other, notebooks in hand. Blinking at one another, they both turned to their pages on their sensei.


Nagisa Kun


Quirk: A snake eyes


When holding a weapon, Nagisa can mask his movements and paralyze his opponents when  close enough. His eyes are also a permanent mutation, causing him to see little details.


Quirk drawbacks:
If he uses his quirk for too long, his movements become sloppy and loud. The paralysis effect stops working, straining Nagisa’s eyes.


“Our sensei is some sort of unkillable teacher. He displays different moods depending on the colour of his face.” Nagisa and Izuku began. “The yellow face he usually wears is his neutral face. When it’s striped green, he’s confident. It also differs when a student gets an answer either right or wrong, being an ‘x’ or an ‘o’. And what’s very interesting is that after lunch time-”


“Yea I don’t need to know that.” Terasaka interrupted. “When he has his most carless face on, one of you will stab him.”


Terasaka handed an object to both of them, whispering something to Nagisa. Without thinking, Nagisa grabbed the object and knife before heading back inside.


After lunch, Izuku’s Sensei was explaining the task for the lesson. They had to make poems and end them with the word tentacles. 


“The flower petals fell like coloured snow. The vines withered up from the ground like tentacles” Their Sensei said, giving them an example. After some time Kayano spoke to the teacher.

“Umm, Sensei? What should we call you?” She asked.


“Well, Kayano why don’t you think of one for me?” Their Sensei replied.




Izuku had noticed it, the octopus teacher had been slow to respond. Nagisa must have seen it too because he took the opportunity to stand up from the desk and go to their teacher. A knife was positioned behind the piece of paper Nagisa was holding. 


Everyone held their breath as Nagisa walked over to their teacher with a small smile on his face. It was kind of strange, someone was about to attempt to assassinate their teacher and they seemed to be happy, not thinking about the actions of doing it.


“Ah, Nagisa. Have you finished already?” Their smiling teacher asked.


Nagisa gave a small nod before rushing in to stab the teacher. 


It didn’t work though, the octopus simply just stopped him with his tentacles with ease. He shook his head in disappointment.


“I’ve told you already, if you want to assassinate me you need a better-” Their teacher was cut off by Nagisa hugging him. “-Plan.”


Terasaka gave a large grin as he pressed a button on a remote, causing a huge explosion. Everyone shielded their eyes as a rain of ‘Anti-sensei’ bullets flew around the room. Terasaka gave out a massive chuckle, explaining his plan and saying that he would pay for Nagisa’s hospital bills with the prize money.


Walking over, Terasaka stopped, looking at the weird sheet that covered Nagisa. Izuku did what he did best, he started analysing it to his best ability, eventually coming to the conclusion that it was the skin of his teacher.


“I actually shed once a month.” Izuku heard his teacher say. His voice echoed throughout the silent classroom. “Good observation, Midoriya! But, I don’t like doing it. The only reason I did do it was so Nagisa wouldn’t get hurt.”


And that’s when they were met with a new emotion. Pitch black, pure anger.


“Terasaka, Yoshida, Muramatsu! This was your plan, wasn’t it?” 


“What!?” Terasaka screamed in defense. “It was all Nagisa and Midoriya’s idea! All I did was press the button!”


Their teacher rushed out of the classroom, returning moments later with everyone's house addresses. 


“It was against the deal for me to harm you, my class but, I could go after all your friends and families.” The octopus grinned before turning an orange colour with a red ‘o’ on it. “I must say Nagisa, you looked so calm and natural up until you grabbed me. And Midoriya! You have some great analysis and I wouldn’t be surprised if you were told to contribute to this plan against your will. After all, you seem to have a great heroes complex.


The rest of you, however. Didn’t take any regard for Nagisa’s safety. So, no more assassination attempts that put your lives at risk, understood? Good."


“A teacher who can’t be killed.” Kayano started. “Sensei means teacher and koro senai means unkillable. So what about the name Koro Sensei?”


Everyone agreed with the name. It was perfect for their teacher. 


They are assassins. Their target is their teacher. Class 3-E, the assassination classroom had just begun. It was going to be a long year...