Shūichirō Kiriyama works at the Limitation Task Force, the place where the cases which have reached the statute of limitations are destroyed. Getting bored of his job, he decides to find a hobby, because it seems important to him to have a hobby. So he decides to puzzle out the unsolved cases on his free time, helped by his coworker Mikazuki, who seems to have a crush on him.
Fuko Kameyama is a first grade high school student and she has a bright personality. One day, cousins Daiya Shinpo and Ichi Shinpo move into an apartment upstairs from Fuko. Daiya has a bright smile. Ichi doesn't talk that much, but he has a warm heart. Fuko wavers between Daiya and Ichi.
