Every 5 years in a specific Japanese-style high school classroom, something causes the death or insanity of students, killing up to one person per month. A surviving student records the events in a diary that the school logs. The thriller will follow the remaining students as they work to figure out what is causing the events. The story is set in a high school where every 5 years something kills or drives students insane in classroom 3-1, with a maximum of 12 deaths per year. A diary is kept of the events and the last survivors will try to solve the mystery of what is causing the events.