13人の麗しきケダモノ

On the day of the school festival, Mamoru and his childhood friend Kanade plus eleven other people consisting of teachers and students are invited into a mysterious event held in the basements of the school church.

After they have arrived an announcement tells everyone to take a seat and states them the rules of the game about to begin. One random person is chosen to be a Devil who hunts villagers at night. Each day villagers must decide on who to execute and the game continues until the real Devil is caught or they manage to kill everyone save for one other person.