A teacher, Atsushi Sugou, is looking for an exchange student to join his class and bring a sense of diversity to the student body. He receives a letter from D-class, a notoriously dangerous class filled with school troublemakers, who write the school's version of Harry Potter fan-fiction where they all kill each other. Atsushi decides to pick Haruhiro, the worst student, to take part in G-class activities. Haruhiro, fearing for his and his friends' lives, decides to kill Atsushi, only to find that Atsushi is invincible. Instead, Haruhiro and his friends join Atsushi in his quest to find treasure that awaits them.