She is the artificially created daughter of Mayuri Kurotsuchi, a combination of his research in artificial bodies and artificial souls. This past has driven her to become rather introverted and passive, preferring to stay silent in her captain's presence. Their relationship is far from the average father-daughter one, as Mayuri does not appear to care much for Nemu's well-being, even using her as bait in combat, and mending her damaged body only when he needs her.