On the third floor of the old school building of Sakuraba Middle School, four girls from the detective agency solved the "not quite right" little things on campus.
A piano that plays automatically in the middle of the night, books that move, and a biological preparation room that has been locked for twenty-three years——
Behind every strange tale, there is a story waiting to be heard.
But in the process of solving the case, they discovered that these incidents all pointed to the same secret.
Intention: Every existence deserves to be seen, and every loneliness deserves to be responded to.