uring the summer vacation period, temporary teacher Kimijima Honoka is in charge of a supplementary class. One day, a female student suddenly jumps off from the school rooftop and mysteriously dies in front of Honoka. Honoka notices a mystery of a student who is not supposed to be there. Honoka has 5 students in her supplementary class including Miura Hitomi and Maekawa Takeru. Honoka soon uncovers a shocking truth of that kid