Chizuru Akitani, daughter of violinist Hiro Akitani, a National Living Treasure, and American Elena, who committed suicide by jumping from the Naruto Bridge, has apparently inherited her mother's depression. With her mother gone and her father remote, 12-year-old Chizuru has little defense against the "black organ" — "a dark presence in (her)chest" — or the class bully, Tomoya Yu, whom she fatally stabs during a psychotic episode.