Zero Woman Namae no nai onna (1997) - 2

Rei, the dangerous but unwilling assassin for the Zero Division regarding the Tokyo Police Department, befriends a young man after she views him cruising a homosexual bar trying to find johns. After he gets beaten up by a team of road thugs, she requires him in to live with her. When a few vicious murders takes place, she starts to suspect that the killer may in fact be her buddy using revenge on everybody who’s got mistreated him. Will she uphold her responsibility to the police, or protect her only friend?