Koro-sensei

homeroom teacher for Class 3-E of Kunugigaoka Junior High School

He claimed to be responsible for creating the permanent crescent moon and said that he planned to destroy the earth after "teaching" Class 3-E for a year.

After being used in experiments, Korosensei acquired the appearance of a yellow bipedal octopus. He is about three meters tall and possesses a large, bulbous head with a large smile and small, beady eyes

Korosensei wears a black academic dress, a small black square academic cap with a yellow tassel, and a large black tie with a yellow crescent-shaped moon on it.