The next morning, Class 3-E was unusually quiet as everyone gathered inside the classroom.
Then the door slid open.
Akira and Erika entered last.
The moment the class saw them—
the entire room froze.
Erika looked bright and refreshed almost glowing, her expression softer than usual. Every now and then, a faint complicated blush appeared on her cheeks whenever she glanced toward Akira. She looked… happy.
Meanwhile—
Akira looked pale, exhausted, and spiritually dead.
And yet somehow—
there was still a faint, satisfied smile on his face.
The entire Class 3-E collectively arrived at the exact same conclusion.
Oh, something definitely happened between them.
Before anyone could say anything—
The classroom window burst open dramatically.
"Nuuhuhuhu~! Good morning, everyone! Did you all remember to bring snacks for today's chemical experime—"
Koro-sensei suddenly froze mid-sentence the instant he noticed Akira and Erika.
His eyes immediately sparkled with dangerous levels of gossip energy.
Then his face turned bright pink.
"Nuuuhuhu… my, my~ You two certainly look happy this early in the morning."
His grin widened mischievously.
"Could this perhaps be related to the titanium handcuffs Sensei saw yesterday~?"
The classroom went completely silent for half a second.
Then—
"TITANIUM WHAT?!!"
Both Akira and Erika instantly turned bright red.
Without hesitation, both of them pulled out anti-sensei knives and immediately launched an assassination attempt on Koro-sensei.
"Nuuuh?!"
Koro-sensei dodged effortlessly while laughing.
"Koro-sensei, don't say weird things like that!"
Erika attacked with terrifyingly perfect form, slashing at high speed.
At the exact same time, Akira moved in sync with her from another angle, trying to flank Koro-sensei.
"Yeah, but it was necessary! Normal handcuffs probably wouldn't have worked on me!"
Erika instantly changed targets.
"DON'T MAKE IT WORSE!"
She immediately started attacking Akira instead.
Akira barely dodged in panic.
"Why meeeee?!"
He instantly ran behind Koro-sensei for protection while Erika chased after him without mercy.
Meanwhile, Koro-sensei desperately tried restoring order despite being the direct cause of the chaos.
"Now, now~! No fighting during class~!"
The rest of Class 3-E watched the entire scene unfold in stunned silence.
Karma was laughing so hard he nearly fell out of his chair.
Nagisa was furiously scribbling inside his notebook.
"He accidentally says extremely alarming things with complete sincerity…"
Okajima looked like his soul had ascended directly into heaven.
Meanwhile, the rest of the class had fully entered scoop mode, whispering among themselves at maximum speed.
"TITANIUM handcuffs?!"
"What exactly happened yesterday?!"
"Were they seriously doing something that required titanium restraints?!"
Among the chaos, Okuda Manami quietly watched the scene with wide eyes, deep in thought.
They're both incredibly strong… And even they still can't kill Koro-sensei… Then how could someone ordinary like me ever manage it…?
After somehow calming both Akira and Erika down—mostly Erika—the class finally settled into their seats, which had now been rearranged for chemistry practical work.
As Akira and Erika sat next to each other as usual, with Akira sticking unusually close to her despite what happened before.
Koro-sensei finished arranging all the chemistry equipment at Mach 20 speed before clapping his tentacles together cheerfully.
"All right! Let's begin today's chemistry lesson!"
He gestured dramatically toward the lab setup.
"Today we will learn about artificial coloring in everyday snack foods and how to separate them. Please follow Sensei's instructions carefully and handle the equipment safely~!"
The chemistry lesson began normally.
Or at least—
as normal as a chemistry class taught by a yellow superorganism could possibly be.
Koro-sensei explained everything enthusiastically while the students followed along with the experiment.
Akira also followed the instructions — after Erika shot him a sharp glare that clearly said "behave."
Still, while completing the assigned work, Akira quietly mixed several extra chemicals off to the side.
He already knew Koro-sensei reacted strangely to chemicals.
So naturally—
he wanted to test things.
Once the main lesson on separating artificial colors finished, Koro-sensei announced brightly,
"All right! That concludes our experiment to extract artificial coloring from snack food! I'll be taking the leftover snacks now~!"
All the students screamed in protest.
"We brought those ourselves!"
Maehara grumbled, "He used this as an excuse to swipe snacks because payday isn't until tomorrow…"
Nagisa thought quietly, Why is a superorganism that can destroy the Earth living paycheck to paycheck…?
Just then—
Okuda Manami timidly approached Koro-sensei while hiding something behind her back.
"U-umm… Sensei?"
"Yes, Okuda-san?"
She nervously brought forward a small bottle.
"Umm… this is poison. Please drink it."
The classroom went silent.
Maehara muttered,
"That's pretty straightforward…"
Okuda looked down hesitantly.
"Is it… too much?"
Koro-sensei's face brightened immediately.
"My! Such an honest assassination attempt, Okuda-san!"
Okuda looked down shyly. "I'm not good at surprise attacks either… but I'm good at chemistry…"
The students started muttering.
"Heart and soul?"
"Okuda?"
Akira muttered to himself, "So it had started, huh…"
Koro-sensei happily accepted the bottle.
"Well then! Sensei shall gladly drink it~!"
He swallowed the first poison.
Instantly—
he began dramatically convulsing.
His skin turned dark blue while cartoonish horns grew from his head.
"Sodium hydroxide. Poisonous to humans, but not to me!"
Then he drank the second poison.
Another dramatic reaction.
This time his body turned bright green while tiny wings sprouted from his sides.
"Ah, thallium acetate, now for the next one!"
Everyone watched in shock.
As he drank the final one and had an even more dramatic reaction and turned grey His face went blank like a tiny emoticon. .
Erika quietly leaned toward Akira.
"What was that one again?"
Akira answered casually.
"Aqua regia. A mixture of hydrochloric acid and nitric acid. It's mainly used to dissolve noble metals like gold and platinum."
Suddenly, Koro-sensei spoke in a completely different voice.
"Even if you hate me… please don't hate assassination."
The entire class collectively thought:
What brought THAT on?!
Then Koro-sensei immediately returned to normal.
"However, Okuda-san, I cannot allow students to manufacture poisons unsupervised. It's dangerous."
Okuda lowered her head quietly.
"…Sorry."
But before Koro-sensei could continue—
Akira suddenly stood up.
Then, in almost the exact same shy posture Okuda had used earlier, he held up two small containers.
"Umm… Koro-sensei?"
The class turned toward him curiously.
"Can you please drink these too?"
Everyone immediately became interested.
After all, this was Akira.
The same person who casually built a functioning Pencil Walker during algebra class.
Koro-sensei smiled brightly.
"Very well! It would be unfair to drink only Okuda-san's experiments~!"
Akira handed him the containers.
"Drink both at the same time."
Koro-sensei did exactly that.
For a moment—
nothing happened.
Then—
another violent reaction suddenly exploded across his body.
Except this time—
Koro-sensei started inflating.
Bigger.
And bigger.
And bigger.
Even as his body rapidly expanded, somehow he remained perfectly yellow.
A second later, his inflated body slowly began floating off the ground.
Koro-sensei tilted his gigantic balloon-like head curiously.
"Hmm? Hydrogen peroxide and potassium iodide?"
Akira said proudly.
"Yep! They rapidly decompose and create a lot of foam. Though honestly, I wasn't expecting this exact reaction…"
But Koro-sensei kept growing larger.
And larger.
His body started crushing desks and pushing tables aside as he expanded.
Akira's eyes widened instantly.
"Quick, Koro-sensei! Before you get even bigger, get outside NOW!"
He immediately rushed to the window and flung it open.
Koro-sensei floated outside into the schoolyard—
still rapidly inflating into a massive floating yellow octopus balloon kaiju.
One of the students suddenly shouted excitedly,
"He's huge! Shouldn't we shoot him now?!"
Akira's eyes widened in horror.
"WAIT—!"
Too late.
Okajima, whose eyes were sparkling with pure destructive excitement, raised his anti-sensei gun.
"Now's our chance!"
Bang!
The anti-sensei BB pellet struck one of Koro-sensei's inflated tentacles.
POP!
The tentacle instantly burst like a punctured balloon.
A gigantic torrent of white foam exploded outward at terrifying speed.
FOOOOOSH!
Foam blasted across the entire playground.
It flooded into the classroom through the open windows like a tidal wave.
Koro-sensei himself began flying uncontrollably through the air like a wildly deflating balloon, spinning violently while spraying foam everywhere.
Akira immediately shouted,
"EVERYONE TAKE COVER!"
He grabbed Erika and dove beneath the nearest bench with her.
Most of the students copied him immediately.
Except Okajima—
who stood completely motionless while getting entirely covered in foam from head to toe.
Finally—
after several seconds of complete chaos—
the giant balloon octopus fully deflated.
A very tiny…
very exhausted…
completely foam-covered Koro-sensei slowly walked back into the classroom with a wet plop.
He sighed deeply.
"…Class dismissed."
After that disastrous chemistry lesson, Erika officially banned Akira from ever using chemical weapons on Koro-sensei again.
Thankfully, Koro-sensei cleaned the entire classroom at Mach speed before the school could somehow collapse into complete anarchy.
It was now a free period.
Some students went outside to play.
Others headed toward the main building.
A few simply wandered around aimlessly.
Meanwhile, Okuda stayed behind with Koro-sensei, quietly working on a new poison formula that might actually affect him.
As for Akira and Erika—
they decided to explore the forest behind the old school building for possible future use.
The two of them walked side by side beneath the quiet trees.
Akira looked around happily.
"You know… this kinda reminds me of when we explored the forest behind our house as kids."
Erika sighed faintly.
"You mean the time you almost burned down the entire forest because you saw a centipede?"
Akira immediately defended himself.
"Yeah… I remember. You can't blame me though. It was creepy. And big."
Just remembering it made him visibly shudder.
Erika smiled slightly, clear fondness hidden in her voice.
"There's one right there."
Akira instantly moved behind her back in a flash.
"WHERE?! WHERE IS IT?!"
Erika sighed again.
"Just leave it alone. It's not bothering us."
As if understanding the conversation, the centipede quietly crawled away into the forest.
Only after it disappeared did Akira finally relax.
Erika shook her head helplessly.
"You're always like this…"
Then, after seeing how absurdly fast he had escaped from the centipede, Erika seemed to remember something important.
Her expression turned more serious.
"Hey, Akira…"
"Hm?"
"How should I fight someone as fast as Koro-sensei?"
Akira tilted his head.
"What do you mean?"
Erika thought for a moment before explaining.
"Even when I can use magic, I'm not really that fast."
She looked down slightly.
"I can't properly keep up with someone faster than me. Without magic, it's even worse."
She continued quietly,
"My Blood Breathing style focuses more on fluidity than speed. And my ribbon combat style feels too dangerous to use against someone as fast as Koro-sensei."
Then she glanced at him.
"And I can't move as fast as you. So I'm not sure how to approach it."
Akira thought about it seriously for a moment.
"Well… yeah."
He nodded.
"Your ribbons are better for area control and pressure. Against someone faster than you, you either need absurd mastery over them…"
He shrugged.
"…or a strong secondary weapon specialized for high-speed interception."
Erika blinked.
"What kind of weapon?"
Akira shrugged again.
"Not sure yet. We'll figure it out eventually."
Then he smiled lightly.
"Don't worry about it."
After a moment, he looked back at her.
"As for your speed… honestly, it's not that hard. I can teach you."
Erika blinked in surprise.
"Teach me? How?"
Akira immediately demonstrated.
"You just stand like this, use your legs like this, breathe like this, and then—"
He took a stance.
Breathed once in a very specific rhythm.
Then—
BOOM.
He instantly appeared several meters away in the blink of an eye.
Akira casually turned back toward her.
"Yeah. Just like that. You just do what I did."
Erika stared at him with complete exasperation.
"I can't follow any of that! Explain it to me first before doing it!"
Akira scratched his head.
"Oh, right."
He immediately launched into a long, detailed scientific explanation about breathing techniques, leg muscle usage, energy circulation, and advanced kinetic theory.
Erika listened quietly.
Then sighed internally.
This is not going to be easy, is it?
By the time school ended, she still hadn't figured it out.
After school ended, Akira and Erika walked home together through the quiet mountain path.
The moment they stepped inside the house—
Ding-dong.
The doorbell rang.
Akira already knew exactly who it was.
He walked over and opened the door to find Koro-sensei happily waving several tentacles.
"Nuuhuhuhu~! As promised, Sensei came to check on the tentacles! How is the homework progressing~?"
Akira blinked.
"That counts as homework?"
Koro-sensei laughed cheerfully.
"Well, it is extremely important homework for the safety of the planet~!"
"…Fair enough."
Akira stepped aside.
"Come in."
He led Koro-sensei directly toward the basement lab while Erika quietly followed behind them.
Once inside, Akira walked over to the containment unit where the preserved tentacles still floated inside the strange blue gel.
The scan results had already fully completed.
Akira glanced over the data one final time before speaking bluntly.
"Basically… this whole thing is stupid."
Koro-sensei blinked.
"Nuuuh?"
Akira pointed toward the scan results.
"They somehow managed to fuse antimatter into your biology. The fact that someone even thought of doing it is stupid. Using something inherently unstable like antimatter in organic things that can die is just asking for trouble. Even though this antimatter is different from normal antimatter, it's still a stupid idea. The one who thought of this was definitely someone who didn't think it through — probably a narcissist who thinks he is the center of the world."
Koro-sensei let out a long "Nuuuh…" and smiled wryly.
"Nuuuhuhu… Sensei cannot entirely deny that…"
Erika crossed her arms.
"Instead of roasting the person responsible, explain what you actually discovered."
Akira nodded and his expression turned more serious.
"As we predicted… if left like this, even though the chances aren't fully 100%, there is still a real chance you will eventually lose control and explode, destroying the Earth."
The basement fell silent.