The first of three perspective characters, Masami Aomame is a 30-year-old fitness instructor who moonlights as an assassin targeting abusive men. She lives an ascetic lifestyle, exercising for hours every day and eating healthily to maintain her frame. This attitude of abstention and self-discipline is an extension of her upbringing; until age 11, Aomame was a member of the Society of Witnesses, a religious cult preaching that the apocalypse is imminent. As an adult, her only indulgence comes once every month or two when she picks up older men for casual sex. Meanwhile, the only individual she loves is Tengo Kawana, whom she has not seen since she was ten years old.

Aomame’s loneliness is a consequence of numerous factors, not least of which is the lack of nurturing and emotional nourishment she received from her parents. Rather than encourage play and affection, her mother forced her to accompany her every weekend to knock on doors and spread the Society of Witnesses’ extremist gospel. In high school, Aomame became close with a classmate named Tamaki. A few years later, however, Tamaki hanged herself to escape an abusive marriage. Using her knowledge of human kinesiology, Aomame murdered the husband by stabbing him in the neck with a tiny ice pick of her own design, leaving behind no signs of foul play.