The forest behind Akira's house echoed with the sounds of high-speed combat.
Akira and Erika chased Koro-sensei through the trees at speeds normal humans could never reach, both wielding twin anti-sensei katanas. Koro-sensei dodged every strike with ease, flying at Mach 20 while laughing smugly, his face covered in green rings.
"Nuruhuhuhuhu~! No matter how fast the two of you become, you will never catch me!"
Akira's slash missed again. He clicked his tongue.
"Don't think this is all I have, Sensei."
Erika followed up immediately, her twin katanas flashing. She had chosen swords over ribbons this time, and with her existing sword skills, she had already begun integrating her Blood Breathing techniques into them. However, she was still getting used to fighting at this speed. Most of her attacks were dodged easily by Koro-sensei.
"I need more training…" she muttered under her breath.
Akira suddenly shouted,
"Follow my lead, Erika! Just as we planned — Star Breathing — First Form: Flashing Comet!"
He exploded forward, breaking the sound barrier as he shot toward Koro-sensei.
At the same time, Erika took a deep breath and activated her own new technique she had just learned.
"Blood Breathing — Fourth Form: Crimson Wind Scattering Petals!"
She rushed in from the opposite side, moving like petals scattered by the wind — fast, sharp, and almost illusory to normal eyes.
But because she had only just learned the form, she lost control and slipped midway.
"W-What—?!"
Instead of hitting Koro-sensei, she smashed straight into Akira at full speed.
Akira's eyes widened, but he didn't dodge.
The two of them tumbled across the ground in a messy heap.
"Ow…"
Erika, now lying on top of him, looked down in panic.
"Oh! Sorry! Are you alright?"
Akira groaned.
"I'm f-fine… b-but can you get up? It's painful."
Erika's face turned bright red when she realized she was sitting on him. She quickly scrambled off.
Koro-sensei appeared next to them, laughing heartily.
"Nuruhuhuhuhu~! Students, that's why I always say to watch where you're going! Now, because of that, I win again~!"
Akira pushed himself up, glaring.
"It's not over yet, Sensei!"
At that moment, a bright purple light suddenly shone down on Koro-sensei, making him stiffen mid-laugh.
Akira immediately rushed in and cut off two of his tentacles.
Erika followed right after, but Koro-sensei recovered quickly, using his hands to push himself backward and escape her follow-up slash.
He looked toward the source of the light.
Hovering in the air was a sleek high-tech drone. On its screen was Ritsu's face, and from the drone came a focused purple beam.
Koro-sensei regenerated his tentacles and asked in surprise,
"Ritsu-kun? Wait… what is that light?"
Akira rushed forward again.
"Don't worry about it, Sensei. You still have me to worry about!"
Ritsu's voice came from the drone.
"Yeah. The assassination continues~"
She flew around Koro-sensei, continuously emitting the purple light to disrupt his movements while Akira and Erika attacked in coordination.
Koro-sensei quickly adapted. Somehow, he pulled out a large umbrella from who-knows-where and used it to block the light.
Akira clicked his tongue.
"Koro-sensei, that's cheating!"
Erika asked in disbelief,
"Where did you even get that?!"
Koro-sensei laughed again.
"Nuruhuhuhuhu~! I just brought it back from the convenience store while you were attacking me!"
Akira clicked his tongue harder.
"I should've made some ring-out rules or something…"
With the light no longer effective, Akira switched plans.
"Move to Plan B!"
Erika and Ritsu immediately coordinated with him.
Erika attacked with her twin katanas while Ritsu used both her light and a built-in gun to force Koro-sensei into a pre-planned path.
Just as Koro-sensei reached the designated spot, he suddenly found himself surrounded by multiple hidden guns.
Koro-sensei tilted his head.
"Using a barrage of bullets is old news, don't you know that?"
Akira pressed a button on a small remote.
"Those aren't bullets."
Several yellow tentacles suddenly shot out from the gun barrels and sliced through the air. One of them cleanly cut off one of Koro-sensei's tentacles.
Koro-sensei stared at his severed limb in shock.
"Nani?! Tentacle guns?! But how?!"
Akira smirked.
"Surprised? I call them Disposable Artificial Tentacle Launchers. They're only half as fast as you, but… there are a lot of them."
Koro-sensei asked,
"How did you even make them?!"
Akira grinned.
"I'll tell you if you survive this."
Koro-sensei started to panic.
"WAIT, WAIT, WAIT! THAT'S TOO MANY TENTACLES!"
Akira winked as he pressed the button.
"Too late. Hasta la vista, Sensei!!"
All the guns suddenly exploded outward, launching a barrage of artificial tentacles from every direction. Koro-sensei was completely surrounded.
Dust exploded into the air as the barrage hit.
Akira, Erika, and Ritsu watched from a distance, waiting in tense silence.
Ritsu tilted her head on the drone's screen, analyzing the results.
"Probability of success: 37.6%."
Erika asked curiously, still catching her breath,
"Did we actually get him?"
Akira immediately cut in.
"Wait, don't ask that — it's a flag. If you say that after a finishing move, your opponent definitely survived."
And as if on cue, Koro-sensei burst out from the settling dust cloud, breathing heavily but mostly unharmed.
"Thank goodness I saved this month's molting. Never thought I would use it here!"
Akira sighed.
"See? He survived that."
Just then, an alarm sounded from Ritsu's drone.
"Time over."
All three of them — Akira, Erika, and even Koro-sensei — let out tired sighs and sat down on the ground.
Akira leaned back against Erika as usual and said,
"Well, today's experiment went well. Thank you for your cooperation as always, Sensei."
Koro-sensei suddenly perked up as if remembering something important. He rushed over and started shaking Akira by the shoulders.
"Akira-kun! First, tell me about those things! What was that light? And what about those tentacles — are they safe?!"
Akira raised his hands defensively.
"Sensei… calm down… I will tell you."
Koro-sensei kept shaking him.
"HOW CAN I CALM DOWN?!"
In the end, Erika and Ritsu had to intervene to pry Koro-sensei off and save Akira.
Once everyone had calmed down, Akira regained his usual composure.
"Now, allow me to explain. That light is a special frequency that, at close range, triggers dilatant behavior in your cells, making your whole body temporarily stiffen instantly."
Koro-sensei listened intently.
"And those tentacles?"
Akira continued,
"Those are just artificial tentacles created from your own cells. They aren't dangerous. The anti-matter in them disintegrates shortly after being exposed to the outside. They're one-time-use only. Look, they're already disintegrating."
Koro-sensei glanced back.
Sure enough, the yellow tentacles were visibly breaking down.
Ritsu asked from the drone,
"These tentacles are really effective against Koro-sensei. Should we use them more from now on?"
Akira scratched the back of his head.
"Yeah… about that. These take a lot of time to make and… I already used my entire stock here."
Everyone turned silent.
Ritsu asked in confusion,
"Wait, so how long will it take to make more of them?"
Akira sighed.
"About that… I need a few days… probably a month… to make a few."
Ritsu asked,
"Then why did you use all of them here?"
Akira turned his face away.
Erika sighed fondly.
"He's always like that — acting first and thinking about what to do later. But he always finds a solution too."
Akira coughed awkwardly.
"Anyway, I will now declare my findings on Koro-sensei's weaknesses in this session."
Koro-sensei perked up.
"Sure, tell me!"
Akira began listing them methodically.
"You are weak to that anti-sensei light — your body freezes instantly. Your molting expends more energy than it seems, and your speed decreases immediately afterward. Your control over your tentacles depends greatly on your mental state. Surprise attacks are really effective, but we are still not fast enough to capitalize on that."
Koro-sensei's face turned orange with a big red "O" of approval.
"Correct! You have completed your homework, Akira-kun. Sensei gives you full marks."
Akira humbly replied,
"It's all under Sensei's guidance."
Just then, Akira's stomach suddenly rumbled loudly.
He placed a hand on it in mild confusion.
"Weird… I shouldn't be hungry right now…"
Erika asked worriedly,
"Are you fine?"
Akira nodded.
"I think maybe I need to eat."
Koro-sensei's eyes sparkled.
"Oh? You're cooking? Can Sensei join in?"
Koro-sensei had become completely hooked on Akira's cooking ever since tasting it once.
Akira stood up.
"Sure. I'll cook. We're having hot pot tonight."
Koro-sensei cheered loudly.
And so, with another experiment successfully completed, the group headed back toward the house with happy and hungry expressions.
---
The next day, it unusually started to rain. Koro-sensei began homeroom with a weird, muffled voice.
"All right, class. Time for homeroom. Please take your seats."
His head was bloated like a balloon for some reason.
Everyone thought the same thing.
That's… big.
Ritsu asked curiously from her screen,
"Koro-sensei, your head is approximately 33 percent larger. Please explain."
Koro-sensei answered,
"Ah, it soaked up all this moisture thanks to the high humidity."
He then squeezed his own head like a sponge, pouring the water into a bucket. Only after that did his head return to normal.
He then looked toward the back of the class where Akira was quietly reading something.
"Akira-kun, no reading manga in class."
Akira looked up.
"But Koro-sensei, I am good at multitasking. I can stay awake reading this and listen to the class too."
Koro-sensei appeared right next to him in an instant.
"Even then, reading manga in class is…"
He glanced at what Akira was reading and froze in amazement.
"Wait… is that the first edition of the first chapter of Dragon Ball?"
Akira proudly held it up.
"Yes. I bought it online after engaging in fierce competition in the bidding event."
Koro-sensei looked concerned.
"Oh, that's great, but is it okay to bring something that expensive to school?"
Akira shrugged.
"Don't worry. What could possibly happen in school?"
Koro-sensei sighed.
"Fine, but it's still not okay to read it in class. Put it away."
Akira closed the manga with a reluctant sigh.
"Okay."
Koro-sensei returned to the podium and continued.
"Now then… Karasuma-sensei told me another transfer student is coming today."
Maehara commented,
"Yeah, well, probably another assassin."
Koro-sensei nodded seriously.
"I got into a little trouble taking our previous transfer students lightly. I won't make that mistake again. In any case, it'll be nice for you to have someone else on your side."
Hara Sumire turned to Ritsu.
"Hey, Ritsu, have you heard anything? You know, as a fellow transfer assassin?"
Ritsu smiled.
"Yes, a little. Originally, he and I were to be introduced together. I would handle long-range attacks, and he, close-range combat. Together, we'd drive Koro-sensei into a corner. But… those orders were canceled for two reasons."
Hara asked,
"Huh… what were they?"
Ritsu answered seriously,
"One, his adjustment took longer than expected. And two… I lack the capacity to provide him support. As an assassin, I am overwhelmingly inferior to him."
The entire class fell silent.
Even Koro-sensei looked serious.
If Ritsu — who had managed to blow off one of his tentacles — was saying this, what kind of monster was this guy?
Just then, the door opened.
A figure clad completely in white robes and a white mask covering his face appeared.
Everyone was shocked, thinking this was the new student.
He held out his hand.
Just as everyone wondered what he was doing, black smoke appeared in his palm, and a pigeon suddenly flew out.
Everyone was startled, but the man laughed.
"Hahahaha! Sorry! Didn't mean to frighten you. I'm not the new kid… I'm his guardian. You can call me… Shiro."
Everyone sighed in relief, except Akira, who was still completely immersed in his manga.
Kayano complained,
"Some guy all in white comes in doing tricks? That'd spook anyone!"
Nagisa added,
"Yeah, except maybe Koro-sen—"
Everyone turned to look at him.
Koro-sensei was plastered flat against the ceiling in his gray liquid form, sweating profusely.
Maehara screamed,
"Koro-sensei, you scaredy-cat!"
Isogai said,
"He's spooked enough to use his liquefy trick!"
Koro-sensei slowly returned to normal and floated back to the podium, still trembling slightly.
"Well, Ritsu-san was telling all those scary stories! N-Nice to meet you, Shiro-san."
He cleared his throat and asked,
"And where is our new student?"
Shiro replied politely,
"A pleasure meeting you, Koro-sensei. He's a rather… unique child, in personality and otherwise. I'll introduce him myself."
He walked over to the podium, pausing briefly when he noticed Akira still reading his manga and Erika quietly trying to get him to pay attention.
He paused slightly.
Koro-sensei asked,
"What is it?"
Shiro smiled faintly and handed Koro-sensei a small box of chocolates.
"Oh, just… you've got good kids here. I'm sure he'll fit right in. Now, to introduce him."
Everyone looked toward the door.
"Hey, Itona! Come on in."
Then, without warning—
BOOM!
The back wall of the classroom exploded.
A short boy with blue-tinted white hair and sharp yellow eyes walked in casually through the debris and sat down at an empty seat.
"I won. I proved that I'm stronger than that classroom wall."
Almost everyone screamed in unison,
"USE THE DAMN DOOR!"
While Akira screamed in pure horror at his now water-splashed manga.
"MY FIRST EDITION FIRST CHAPTER OF DRAGON BALL MANGA!!"
Itona ignored the chaos around him and said flatly,
"That's all that matters… that's all."
The entire class had the same thought.
Gah, we've got ourselves another handful!
Even Koro-sensei had a slightly strained expression at the unfolding situation.
Shiro stepped forward calmly.
"His name is Horibe Itona. Please, call him Itona."
Before anyone could react further, Akira shot up from his seat, face twisted in anger. He stomped straight over to Itona.
"Oi, Itona! You have some guts wetting my manga!"
Everyone collectively thought,
That's what you're worried about?! There's a giant hole in the wall!
Itona stood up slowly, staring at Akira with cold yellow eyes.
"You might be the strongest one in this class. But don't fret. You're weaker than me, so I won't kill you."
Akira's presence shifted. A quiet, heavy pressure filled the classroom as he stared Itona down.
"Oh? You think you're stronger than me?"
The air grew thick.
Karma leaned forward with interest.
"Oh? Are they going to fight?"
Maehara grinned.
"Oh, is it? The strongest transfer student of today versus the strongest transfer student in history!"
Just as it looked like they were about to clash, Koro-sensei suddenly appeared between them.
"Alright, stop it! No fighting between students in class!"
Akira complained immediately,
"But Sensei, he wet my manga!"
Erika quickly intervened. She grabbed Akira's hand and pulled him back.
"Alright, calm down. We can still save the manga."
Akira grumbled but relented.
"Fine…"
He turned back to Itona with a sharp glare.
"I'll deal with you later."
Erika led him back to his seat, where they immediately began emergency manga rescue operations.
Erika carefully dried the pages with tissues. Akira was already calculating optimal moisture evaporation rates in his head. Koro-sensei offered some tissues with a worried expression. Even Ritsu extended a small dryer from inside her unit to help.
Itona watched them for a second before saying indifferently,
"Do whatever you want. It doesn't matter."
He walked straight toward Koro-sensei, who was back at his podium.
"I only want to kill those who could be stronger than me. And in this classroom, Koro-sensei… that's you."
Koro-sensei was casually eating chocolate at his podium. He looked up with a calm smile.
"Do you mean strong and weak in terms of fighting, Itona-kun? If it's a trial of strength, you and I aren't even in the same dimension."
Itona took out the exact same chocolate Koro-sensei was eating and held it up.
"Sure we are. After all… we're brothers by blood."
The entire class froze in stunned silence for a split second.
Then they exploded.
"EHHHHHHHHHHHH?! B-B-B-B-BROTHERS?!"