The teenage assassin Sawa discovered the man behind her parents' deaths was her own her foster-father, the police detective Akai. She murdered him. Years later, her whereabouts are still unknown. The story of a new killer has begun to circulate around the city. She is called the Angel of Death. She eliminates her targets with grace and precision, and then vanishes without a trace into the darkness. By day, the Angel of Death wears a different face; the face of Monaka, an ordinary high school girl. But she seems so delicate and sensitive, can it really all be an act? Her past is tied with Akai, and her fate is a duel to the death with the one man who can protect her - the one she loves most. Which heart is real? The icy heart of the Angel of Death, or the kind heart of Monaka?