Third-year middle school student Koki Midorikawa spends his summer vacation with a deep sense of frustration. When his enigmatic classmate Atsushi Hoshino invites him to co-write a detective story, a new teacher, Haraguchi, is also trying to identify a student from his school who appears to be visiting a suicide website. The students' and teachers' separate loneliness gradually converges into one mystery.

A coming-of-age mystery where loneliness and writing meet during the summer of ninth grade.