C³

Haruaki Yachi receives a heavy black cube from his father abroad, then discovers a girl named Fear in his home during the night. She is the human form of a cursed instrument, burdened by a history of suffering and seeking release from the curse that binds her to it.

Haruaki tries to help her build a different life through kindness rather than harm. Their efforts are interrupted by groups determined to possess or destroy her, and by other cursed objects whose histories bring new dangers. Protecting their home becomes inseparable from confronting the past Fear wants to escape.