She is the older sister of Reiji and daughter of Haruka. She kills herself to deprive a taker of the satisfaction of killing her, with Reiji's sorcery device. In doing so, she was able to make a contract with the same device as Reiji. She consequently shares her Life Points with Reiji. She was born psychopathic, and has a brother complex, leading to situations that indicate a need for an incestuous relationship with him.

She is a top student at high school, but sleeps in the breaks between classes. Because of the sorcery device, she cannot die by normal means, only when her life points run out (expiring one each day). After Ayaka melds with Reiji, she has 5 life points. She is a Psychopath class taker.