Kite Liberator (2008) Anime Watch

In the previous series "Kite," a killer—Sawa—suddenly disappears after she avenges her parents' death, and no one knows where she is.

Several years later, a figure dances airily on the dark side of a big city. She is an angel of death, killing her victim gracefully and disappearing.

Monaka is a normal high school student, though this quiet and modest life has a darker side. An angel of death is Monaka's other persona.