Nobuko Izumi is the mother of Shinichi Izumi and the wife of Kazuyuki Izumi. She is a housewife who provides a warm and stable home environment for her son. Nobuko is a caring and attentive parent, frequently expressing concern over Shinichi’s increasingly withdrawn and unusual behavior as he struggles with his parasitic infection. She represents the normalcy and security of family life before the arrival of the parasites. Her primary motivation is the well-being of her son, and she strives to maintain a close, affectionate relationship with him.

Nobuko’s role in the story is brief but pivotal. Early in the series, she is attacked and killed by a parasite that decapitates her and takes over her headless body. The parasite, in need of a new female host after its previous body was fatally injured, uses Nobuko’s corpse to impersonate her. When Shinichi encounters this creature, he is forced to confront the horrifying reality that his mother is dead and that the body before him is merely a vessel for a hostile entity. The parasite, mimicking Nobuko’s mannerisms, stabs Shinichi through the heart when he refuses to accept the truth. Shinichi survives only because Migi, his own parasitic companion, performs an emergency repair. The parasite is later killed by a combination of Shinichi and Mamoru Uda, ending the impersonation.

Nobuko’s death and the traumatic encounter with her parasitic double serve as a turning point for Shinichi. It shatters his sense of safety and deepens his understanding of the parasitic threat, fueling his determination to fight back. Her memory becomes a powerful emotional anchor, symbolizing the innocent lives he seeks to protect and the personal loss that drives his transformation from an ordinary teenager into a hardened, resolute individual. Nobuko herself has no supernatural abilities; her significance lies entirely in her role as a loving mother whose tragic fate profoundly shapes the protagonist’s journey.