C3

Yachi Haruaki, a high school student, is given a mysterious, extremely heavy black cube by his father, an archaeologist working abroad, at the beginning of the story. The following night, Haruaki awakens to a strange commotion in the kitchen and finds a little child with blue hair stealing rice crackers while completely naked. Haruaki assumes that the girl, who calls herself as "Fear" (pronounced "Fia" in Japanese), is the cube that his father had sent. Fear says that she is a Cursed Tool, an item that was once employed by people to gratify their terrible impulses. They eventually acquired human traits at a high cost, including the ability to experience human emotions and cause uncontrollable harm to others. She is reassured by Haruaki that he is immune to any curse she might impose upon him, and he makes a promise to assist her by lifting her spell. Together with her strict class representative Kirika Ueno and next-door neighbor Konoha Muramasa, they work to assist her break her curse. However, she becomes embroiled in numerous risky organizations and other Cursed Tool situations as a result of their efforts.