Earth is threatened by a powerful monster that destroyed 70% of the Moon with its power, leaving it permanently in the shape of a crescent. The monster claims that within a year, the Earth will also be destroyed by it, but offers humanity a chance to avoid that fate. He himself begins to work as a teacher in class 3-E of Kunugigaoka High School, whose students have the objective of assassinating him. The Japanese government promises a reward of ¥10 billion the monster is called korosensei