Only Koro-sensei was able to see the Class E pupils for who they truly were, and he exerted every effort to help them develop their talents and get support and encouragement.
Koro-sensei truly assisted them in identifying and honing their strengths while everyone else was preoccupied with their flaws and academic deficiencies.
However, he wasn’t always this way, you know.
In actuality, Koro-sensei began as a charming human assassin with no heart. Koro-sensei was quite a handsome man when he was a human. Koro-sensei was quite the beauty, with fair skin, dark eyes, and short raven hair.
Additionally, he took care to maintain a pleasant, sympathetic, and cordial grin at all times. This fake smile was merely a ruse to cover up the murderous killer he was.
He dressed professionally while working, just like a typical salaryman would.
When he was apprehended, he had to don a patient scrub, yet he still managed to look good in it.
When he is upset, traces of his assassin nature emerge. He then turns to his go-to method of instruction, which is fear rather than empathy.
How did Koro-sensei become the person we know and adore?
A child was born in a ghetto, where he had just one source of knowledge and trust. An individual dies if they are killed.
This child would have been loving and caring if it had been raised in a better environment.
This youngster chose the only route he was familiar with and thought led to an assassin’s death.
This assassin was skilled in eliminating any foe. Kill the powerful with knowledge. Kill the clever with force and skill. And even those who had both succumbed to his spell.
This assassin had slain so many targets with such success that he became known as “The Reaper.” The reaper kept on killing till he came across a young child who asked to be his pupil.
Any information, abilities, and tactics that the Reaper possessed—including all of them—were imparted to his pupil. He performed well with his student.
The Reaper, on the other hand, had no faith in him and merely saw him as a tool for his purposes. They had a task when it was shown that the Reaper was correct.
His pupil deceived him, falsely accused him, and fled.
Nobody would care if he passed away because he was an orphan with no recognized life and his occupation as an assassin.
Yanagisawa grabbed The Reaper and used it as a test subject while he was working with antimatter.
He would frequently inject antimatter into the Reaper to test how it would affect him and his body.
The Reaper’s body began to respond to the antimatter in various ways as the amount in his body continued to rise slowly and gradually.
He acquired superhuman abilities like regeneration, poison immunity, extreme defense form, and super speed.
Aguri, who was betrothed to Yanagisawa, was encountered by the Reaper at the lab. Since she didn’t have a romantic relationship with her fiancé, he did not first consider her to be anything, not even a prisoner.
Aguri and the Reaper continued talking as time went on; she came to appreciate his benevolence and he realized that all of her shortcomings contributed to her appeal.
If the Reaper didn’t have to endure all the hardships that he did, Aguri said, he might be a bit perverse with a good heart, a little petty, and a little stubborn.
She was a teacher who frequently spoke about her pupils and how she tried to assist them but was unable to.
She also pointed out that the Reaper might make a fantastic teacher. The Reaper first understood the meaning of mercy and compassion through her. Though not for very long.
Sensei Koro’s Demise
Yanagisawa sent a lunar experiment to examine the presence of antimatter in living things. Antimatter was given to a lab rat before it was launched to the moon. As a result, the moon lost 70% of its mass.
Yanagisawa understood that what he had created was effectively a ticking time bomb. In other words, the Reaper was a ticking time bomb that would detonate in another calendar year.
He quickly gave the order to kill the Reaper. Aguri, who had been made aware of everything, hurried and informed the Reaper.
The Reaper quietly informed her that he believed death was imminent. He went on a violent spree, killing everyone he saw as a result.
Yanagisawa made every effort to stop him, but the Reaper was now unbeatable due to the talents he had attained.
The Reaper intended to descend to earth and obliterate it. From behind, Aguri grabbed hold of him and stopped him.
However, this set off a trap in the demolished structure, and a tentacle sliced through her stomach.
He begged the Reaper in her final moments to assist the pupils in Class E since he would be a fantastic teacher.
Despite being deeply grieved by her passing, the Reaper didn’t give up. He made the offer to teach Class 3-E.
He removed Aguri’s crescent moon off her top and fastened it to his tie. He put on a coat and a graduation cap with a golden tassel.
Aguri had already given the Reaper his birthdate but not his name. As soon as Sensei entered the classroom, he asked the students to name the person they had to kill but were unable to.
Then Kaede abbreviated “Korosenai Sensei,” also known as “Unkillable instructor,” to “Koro-sensei.” This is how Koro-sensei evolved into the beloved Koro-sensei that we know today.