A mysterious creature destroys part of the moon and then warns that, if it is not destroyed before March of the following year, Earth will be next. It also demands to become the homeroom teacher of Class E, a third-year class at Kunugigaoka High School.

A mysterious creature destroys part of the moon and then warns that if it is not destroyed before March of the following year, Earth will be next. It also demands to become the homeroom teacher of Class E, a third-year class at Kunugigaoka High School. As the deadline for the assassination and the date of the end of the world approach, the students discover their true abilities and Koro-sensei's shocking identity.