The tentacles spoke to me, asked what I wanted to be. To be weak I said, to be flawed, vulnerable. To perceive weakness in others not to exploit but to protect. To be a guide, to be a teacher."

Teaching Ability: With his immense intelligence, he was able to single-handedly teach multiple academic subjects and produce impressive results from Class 3-E. His incredible mentality combined with his speed also allow him to multitask on up to dozens of jobs at a time, all of which seemingly being done simultaneously (including providing individual teaching to every student of Class 3-E simultaneously, focusing on the subject each of them needs to study most and even changing his headband as he goes). His apprentice, whom he met killing his father. After witnessing the killing, the child became enamored and requested that the Reaper train him as his apprentice. Eager for the assassination opportunities that an apprentice could give, the Reaper took in the boy and trained him.Korosensei has the appearance of a yellow octopus. He is about three meters tall and possessed a large, bulbous head with a large smile that rarely breaks or moves and small, beady eyes. He uses two tentacles as arms, each having two feelers as fingers, and utilized the rest of seemingly jelly-like limbs - his tentacles - to walk. Korosensei has a pair of hidden nostrils, which make him appear to have four eyes if detected. Due to his constant grinning, he can change his color depending on his emotions.

Korosensei is usually represented by an octopus due to his appearance of his head and tentacles. Aware of this, he often draws octopus mascots when scoring exam marks and makes jokes about octopuses.To Class 3-E after telling his past) " If I'm going to be killed, it can't be at the hands of anyone else. I want to be killed by you." The difference between the novice and the master is that the master has failed more times than the novice has tried." Within the UK and USA the price you see is the price you pay - you won't be charged any extra fees. Regeneration: If one or more of his tentacles are maimed, Korosensei can regenerate the severed limb. However, this weakens his stamina.

Honestly, there isn't much meaning to the splendid names given to you by your parents. What does have meaning, is what the person behind that name does during their actual lifetime. The name doesn't make the person. The name simply remains gently within the footprint left on the path a person walks." However, during the escape, Aguri is mortally wounded when she landed in the line of fire of a special tripmine meant for him, to the latter's horror. He then laments that if he hadn't wasted his skills on killing, he would know how to save her. Her final wish to him was to teach the students of Class E, all while thinking of what a wonderful teacher he will be. Depressed but not broken, the Reaper vowed to help those children. He took the tie Aguri got him, left a note, left the facility for a nearby mountain, and then used various items on the mountain to create a new set of clothes to suit his new role as a teacher.Superhuman Speed: Korosensei can travel up to the speed of Mach 20. His normally soft and jelly-like head hardens under immense pressure as a process known as the dilatancy phenomenon, which presumably lowers his wind resistance, allowing him to reach inhuman speeds. The only known objects to surpass this are the reusable space shuttle and the transformed Reaper. Korosensei then collapsed out of fatigue from his fight with Reaper 2.0, and after noticing the laser's light intensifying, he announced that now was the time for the class to kill him. Once the class reluctantly decided to pin him down, Korosensei tells his students that he left them each a book of advice as a farewell gift and that he would announce one last roll call. As he calls out the list of names, he reminisces how he is proud of his students who gave meaning to his life. On the final night of the deadline, Korosensei and the class happily reunited. Briefed of the situation and that the satellite weapon would fire again in 90 minutes, he imparts one last life lesson to his students - to confront and navigate through society head-on and not reject it as he once did. Rio Nakamura presents their teacher with a small cake to mark the event Aguri declared to be his birthday (the day she and Korosensei first met each other). Having not eaten any sweets for nearly a week, Korosensei starts drooling on the cake but nonetheless feels happiness. However, before he could blow out the candle, the cake was destroyed by Shiro, accompanied by Korosensei's former apprentice (No. 2), who is now a hideous tentacled monster. To Class 3-E) "As you go through life, the mighty current of society is bound to get in your way, and there will certainly be times things don't go as you'd hoped. When this happens, do not look to society for a cause. Do not renounce society. Frankly, you'd be wasting your time. Instead, just say, "That's life!" and muddle your way through with frustration."

However, after meeting Aguri Yukimura, he finally knew what compassion really was--becoming much more kind and compassionate. According to Aguri, if he was born in a peaceful country, he would be "a little lecherous, smart, klutzy, kind of stingy, and stubborn" and he would smile because he is a genuinely a kind person. [3] This prediction happens to reflect his personality; which became forefront after he answered the tentacles. Before leaving the island, Korosensei organized a Test of Courage. It is supposed to be a haunted attraction, but his ulterior motive is to create more juicy gossip by pairing up the students to spark any romances. The class immediately realizes what Korosensei had planned, and the latter half of the pairs instead turned the tables on their teacher by making him scared. To Nagisa Shiota) "The fact that I'm targeted by everyone is proof that I'm powerful, after all." [12]

Superhuman Digestion: Korosensei can digest anything aside Anti-Sensei weapons, as his teeth can crush any hard materials. Whether he eats something or it enters his body, he can either melt the food first, then eject it, or it will just be digested. Although it is not guaranteed that Korosensei will receive no irregularities from what he has eaten, it usually has no tactical disadvantages if it is not a weakness for him. When first introduced, Korosensei was an upbeat individual who demanded absurd and seemingly mundane requests despite claiming he would be the cause of the planet's destruction in a year. He was also rather kind to others in general and could switch from silly and childish to serious on the fly. According to Nagisa, Korosensei also was unintentionally petty at others at times and loved gossip, both traits heavily noted throughout the series. It was there that he met and befriended Aguri Yukimura, a teacher who was at the time in an arranged and abusive marriage to Yanagisawa. She was brought in to keep a closer eye on him as Yanagisawa considered her easily expendable if he attempted to break free and take her hostage. As the tests continued, the Reaper began to slowly bond with her and became fond of her as she worked on compiling exam questions for her class, and it was during this time he learned what compassion was.