Arc 1: The Ranking Coup
The pain was non-existent.
There was only an overflowing sense of relief, warm and enveloping, like soaking in a hot spring after a long day of correcting stacks of exam papers. Sunlight filtered through the leaves of the old wooden schoolhouse, casting dancing shadows across the faces of his students.
"Goodbye, Koro-sensei."
Shiota Nagisa's voice trembled, yet it was filled with resolve. The anti-sensei knife pierced his vital point, right through the crescent-moon tie—the gift from Aguri.
He smiled. It was his signature wide, satisfied grin. He had completed his duty. He had raised them well. He had kept his promise. As particles of light began to separate from his octopoid body, drifting toward the sky, he closed his eyes.
Rest now, he thought. You've worked hard.
Darkness welcomed him. Silent. Peaceful.
Then, suddenly, his lungs jerked, greedily inhaling oxygen.
His eyes snapped open.
It wasn't the blue sky above the old Kunugigaoka school building that greeted him, but the sterile white ceiling of a hospital room. The sharp scent of antiseptic stung his nose, replacing the smell of earth and rotting wood.
He tried to move his tentacles, but what moved were ten human fingers. Pale skin, bones that felt fragile yet undeniably real. He bolted up in a panic, searching for a mirror.
In the reflection, a teenage boy stared back. The face was familiar. It was the face he possessed before he became a monster, before those mad experiments stripped him of his humanity.
It was the face of The Reaper. The face of a legendary assassin.
However, the eyes were different. They were no longer cold and empty as they once were. There was a lingering warmth there—the eternal remnants of the lessons learned with Class 3-E.
"Seiji," a nurse called out softly. "Koroizumi Seiji-kun? Are you awake?"
The name felt foreign on his tongue, yet his memory pulsed, accepting this new identity like water flowing into an empty vessel.
This world was not his world. It was a similar Earth, yet distinct. There was no moon destroyed by 70%. There were no tentacles. There were no super beings.
He smiled, a small smile holding a thousand meanings.
"Yes," he answered quietly. "I'm awake."
.............................................
Years passed with deceptive speed.
To the world, Seiji Koroizumi was merely a somewhat eccentric orphaned genius. But behind the closed doors of his modest apartment, he was reconstructing a legend.
Seiji sat before three brightly lit monitors in a darkened room. His fingers danced across the keyboard at a speed the human eye could barely track.
"Data synchronization complete, Sir," a cheerful voice chimed from the speakers.
On the main screen, the 2D avatar of a girl in a school uniform appeared.
"Good work, Ritsu," Seiji praised.
"Thank you! Though, my name in this source code is 'R-2', you know," the AI protested. Seiji had rebuilt Ritsu from his memories of programming logic and Machine Learning algorithms he had once studied. The Ritsu of this world didn't possess an artillery body, but her reach within the cyber world was far more terrifying.
"You're still Ritsu to me," Seiji chuckled, taking a sip of his sweet tea. "So, what's the status of Japan's underworld right now?"
Ritsu's face turned into a pout. "Disappointing, Sir. Statistics show a drastic drop in quality compared to the data from your past life's memories. No God of Death. No Lovro. The hitmen here... well, they're sloppy. Most are just thugs handed a pistol."
Seiji let out a long sigh. He leaned back in his chair.
Since realizing he was in a new world, he had trained this human body relentlessly. He relearned biology, sharpened his martial arts reflexes, devoured books on quantum physics, and honed his killing instincts until they were razor-sharp. He wanted to be ready.
Ironically, however, this world didn't need a super assassin.
"This world runs on the wheels of politics and intrigue, not pure violence," Seiji murmured, his eyes scanning the data on politicians' dirty money flows displayed by Ritsu. "Killing someone physically is easy here. But killing someone's character, destroying their future without laying a finger on them... that is the 'assassination' glorified in this world."
He stood up, walking toward his apartment window overlooking the hustle and bustle of Tokyo.
During junior high, he rarely attended school. To him, the standard curriculum was too boring. He chose to travel around Japan, skipping class as he pleased, looking for something to satisfy his thirst for a challenge, or perhaps... looking for someone who needed saving.
Because deep down, the soul of the Sensei still lived alongside the soul of the Reaper.
Seiji picked up a tablet from his desk. On it, Ritsu had compiled several profiles—people he had accidentally crossed paths with during his truancy tours across Japan. Small interactions that shifted destinies.
He swiped the screen to the first profile.
[Target: Karuizawa Kei]
His memory drifted back to a narrow alley a year ago. Rain was pouring heavily, masking the sound of sobbing.
The girl, Karuizawa, was being cornered. Not by thugs, but by her own classmates. Brutal bullying. Her gaze at that moment was empty, broken, as if she had accepted that she was an eternal victim.
Seiji didn't jump down and beat up the bullies hero-style. That was too cliché. Instead, he emerged from the darkness with a black umbrella, his aura so chilling that the bullies fled in terror without him needing to touch them.
The girl trembled on the ground, covering the scars on her body.
"Those scars are ugly," Seiji had said at the time, his voice flat but piercing.
Karuizawa flinched, her eyes betraying anger and shame.
"However," Seiji continued, crouching before her, "those scars are proof you survived. You are not a victim, Karuizawa-san. You are a survivor. Don't hide your fangs behind a fake smile. If the world wants to eat you, make sure you poison them first."
That day, Seiji didn't just save her. He taught the girl how to manipulate the fear of others. He saw a small fire ignite in Karuizawa's eyes before he left.
Seiji swiped the screen again.
[Target: Ichinose Honami]
The girl who was too kind. The girl who almost destroyed her own life for a hair clip meant as a gift for her sister.
Seiji caught her hand just as she was about to take the item in the shop. Not to report her, but to stop her.
"Stealing is inefficient," Seiji whispered in her ear, causing the girl to freeze. "You're trading a future worth billions of yen for a hair clip worth a few thousand? That is bad math."
Seiji dragged her out (metaphorically), then sat with her on a park bench. He didn't lecture her on empty morality. He taught her entrepreneurship.
"If you need money, create value," Seiji said, drawing a simple business scheme in the dirt with a twig. "Your charisma is your weapon. Use it. You could sell ice in the North Pole if you wanted to."
Ichinose Honami didn't steal that day. Instead, she learned how to be a leader who empowers. Seiji only hoped her naive kindness had evolved into something more resilient.
The screen swiped again.
[Target: Shiina Hiyori]
There was no conflict here. Only tranquility. A quiet city library.
The two of them often sat opposite each other without speaking, each immersed in a thick book. Hiyori loved mysteries; Seiji loved classic literature and science.
One day, the girl asked, "Does knowledge make you happy, Koroizumi-kun?"
Seiji closed his book, offering a faint smile—a smile akin to Koro-sensei's. "Knowledge is the only power no one can steal from you, Shiina-san. And sharing knowledge... that is the highest form of affection."
They were friends in silence. A pure intellectual connection.
[Target: Horikita Suzune]
The stubborn girl. The girl living in her brother's shadow.
Their meeting took place in a public dojo. Suzune was training desperately, her movements sharp but stiff. She challenged Seiji because she noticed him observing her practice with an analytical gaze.
It was a crushing defeat for Suzune. Seiji didn't use strength; he simply redirected the girl's power back at her. Master-level Aikido.
As Suzune panted on the floor, frustrated that she couldn't even touch the hem of Seiji's shirt, he spoke:
"You fight like you're imitating someone else. Your brother's shadow is too large, so large that you can't even see your own hands."
"What do you know?!" Suzune snapped.
"I know that a copy will never surpass the original," Seiji replied coldly. "Be yourself, Horikita Suzune. You have the potential to be something different, something more terrifying than just 'Manabu's little sister.' Stop chasing his back and start walking beside him."
That was the first time Horikita Suzune admitted defeat to someone her age.
[Target: Kushida Kikyo]
And finally... the two-faced girl.
An incident in her junior high class had nearly exploded. Kushida was ready to destroy everything, leaking everyone's secrets due to accumulated stress. The class was on the brink of total collapse.
Seiji walked into the storm casually. He locked Kushida in an empty classroom before she could deploy her "bomb."
Kushida raged, cursing with her true, horrific face. But Seiji only laughed.
"Keep screaming," Seiji said. "I like this face. It's far more honest than your angel mask."
Kushida fell silent, confused.
"You're tired, aren't you?" Seiji approached, unintimidated. "Being an angel is exhausting. But destroying everything will only leave you alone in hell. You need a vessel to dump your poison, Kushida-san. Don't blow up your class. Make me your trash can if you need to. Or better yet... use those two faces of yours as a weapon. It's a talent, not a curse."
Seiji managed to diffuse the explosion. The class was saved, though they never knew who saved them. And Kushida... she learned fear and respect for this young man named Seiji.
"Sir," Ritsu's voice broke Seiji's reverie. "The acceptance letter has arrived."
Seiji set down his tablet. On the desk lay a thick envelope sealed with red wax.
Koudo Ikusei High School.
Tokyo Metropolitan Advanced Nurturing High School. A school established by the Japanese government with the goal of fostering the future generation that would support the country.
"The analysis of this school is fascinating," Ritsu displayed a graph on the monitor screen. "100% employment and university placement rate. Luxury facilities. The S-Point System. And most importantly... its educational methods."
Seiji's eyes narrowed. "Very similar, isn't it?"
"Similar to Kunugigaoka under Asano Gakuho's leadership," Ritsu confirmed. "Absolute competition. Hierarchy. And freedom restricted by invisible rules."
Seiji chuckled softly. "Nurufufufu..." His old signature laugh slipped out unconsciously. "Asano-kun would surely love this place. Or perhaps he'd hate it because he isn't the Student Council President."
He opened the envelope. Inside, his acceptance status was printed.
Name: Koroizumi Seiji Class: 1-D
"Class D," Seiji read.
"Based on academic data, you scored perfectly on all entrance exam subjects," Ritsu explained. "However, your attendance record in junior high was terrible. Furthermore, your psychological interview results were rated as 'hard to read' and 'uncooperative.' The system placed you in the lowest class—the dumping ground for defective products."
Defective products.
Those words made Seiji's smile widen.
In his previous life, he taught the End Class (Class E). The class that was discriminated against, the class considered garbage. And he turned that garbage into assassins capable of killing the fastest creature on Earth.
Now, fate had placed him back in the same position. But this time, not as a teacher, but as a student.
"They judge a book by its cover," Seiji murmured as he stood, picking up the maroon uniform jacket that had been prepared. He put it on. It fit perfectly.
He looked at his reflection in the mirror. He looked like an ordinary elite student. Frail. Harmless.
But beneath that uniform lay the memory of thousands of assassination techniques. A brain capable of processing information like a supercomputer. And the heart of a teacher who longed for a challenge.
"Ritsu, download all school maps and student data for this year to my phone," Seiji ordered.
"Done three seconds ago, Sir."
Seiji smirked. "Good."
He picked up his bag. There were no weapons inside. Just textbooks and a packed lunch. His best weapon was himself.
The morning was bright when Seiji arrived at the bus stop heading to the school.
Many students in the same uniform were gathered there. Faces full of hope, arrogance, and anxiety.
Seiji stood at the back of the line, observing. He watched the colors of their emotions.
Then, his eyes caught another figure.
A young man with brown hair and eyes that were... dead.
The young man stood with a posture deliberately made to look relaxed, but Seiji could see it. Perfect body balance. Micro-vigilance in every muscle movement.
That wasn't the posture of an ordinary student. That was the posture of someone trained.
Their eyes met for a split second.
The young man—Ayanokouji Kiyotaka—showed no reaction whatsoever. But Seiji knew, the boy's instincts must be screaming that there was "something" off about Seiji.
Seiji gave a friendly smile, the smile of an "ordinary student." Ayanokouji gave a small, almost imperceptible nod, then looked away.
"Interesting," Seiji whispered softly, his voice barely audible amidst the roar of the approaching bus.
The bus stopped. The doors opened.
This wasn't just a school. It was a battlefield. It was a miniature political ecosystem where the strong preyed on the weak, and the smart manipulated the foolish.
But they didn't know one thing.
They had just invited a monster into the sheepfold. A monster who once destroyed the moon, and a monster who loved his students more than anything.
Seiji stepped onto the bus.
"Class is in session," he murmured.
And with that, his school life—at Koudo Ikusei High School—officially began.