Korosensei

Korosensei is the homeroom teacher for Class 3-E of Kunugigaoka Junior High School, and the central character and main antihero of Assassination Classroom. Korosensei claimed to be responsible for creating the permanent crescent moon and said that he plans to destroy the earth after "teaching" Class 3-E for a year. Prior to being a teacher he was the master assassin known as the "Grim Reaper ."

Korosensei has the appearance of an octopus. He is about three meters tall, and has a large, bulbous head with a large smile and small, beady eyes. He uses two feelers as arms, with two fingers each, and uses the rest of his tentacles to walk with. He wears a black academic dress, a small black square academic cap with a yellow tassel, and a black tie with a yellow crescent-shaped moon on it. As a human he had black hair that reached to his nape and dark eyes. He was notably attractive and was described as having a smile kinder than anyone else.

Korosensei is very smart to the point that he can teach almost every subject by himself. He loves sweets almost to extreme cases and is also shown to be a very perverted character, a trait he shares with his student Okajima. He is also rather kind, and can switch from silly to serious on the fly. One of Korosensei's attributes is the fact that he is able to connect to each student individually. This is the reason why all the students respect him despite the fact that he is going to blow up the Earth in a year. According to Aguri Yukimura, if he was born in a peaceful country, his personality would be "someone a little perverted, with a good head but a few screws loose, petty about small things, and also a lot stubborn... or something like that." He has/would have "a gentle smile not just for business, but because he is a gentle person himself." This prediction happens to reflect his current personality which became forefront after he answered the tentacles.