Shotaro is an average kid, but when he’s with Sakurako, they find dead bodies. Under Sakurako’s orders, Shotaro unearths a human skull, leading to another mystery!

Shoutarou finds a little girl at a convenience store in the dead of night. Other than her nickname, Ii-chan, no one can figure out her real name and address. Finding a bloody handprint on her backpack, Shoutarou asks Sakurako for help. But their inquiries only lead them to a shocking realization...

While on a bone-hunting expedition in the mountains, Sakurako and Shoutarou again find the skeletal remains of a human being. Later, Shoutarou finds out that the body belonged to Kougami's grandmother, whose death the police have written off as a suicide. In disbelief, Kougami asks Sakurako for help...

Police Officer Utsumi asks Shoutarou for a favor. His friend, Fujioka, is afraid of a curse where all the men in his family die at an early age. Utsumi asks for Sakurako's help in persuading Fujioka that the curse is non-existent.

The cause of Fujioka's ill health is found to be mold growing on the painting that had been placed in his study at the suggestion of a certain artist. As everyone sighs in relief, there is a sudden commotion in the yard...

While at a summer festival, Kougami is separated from her friends. She happens to catch sight of a woman standing on the bridge. Clad all in black, there is something off about her... As Kougami suspects imminent suicide, the woman vanishes, leaving an ominous letter and a diamond ring behind. Determined to prevent her death, Kougami asks Isozaki and Utsumi to help her find the woman...