With graduation 10 days away, homeroom teacher Hiiragi gathered all 29 students of class 3-A and proclaims them his hostages. His last lesson regards the death of a student that passed away a few months before. Nobody will be able to graduate until the truth is known.

With graduation 10 days away, homeroom teacher Hiiragi gathered all 29 students of class 3-A and proclaims them his hostages. His last lesson regards the death of a student that passed away a few months before. Nobody will be able to graduate until the truth is known.