Mitsuko Momochi is a supporting character in the anime Housing Complex C. She is a middle-aged woman who lives in the seaside housing complex with her son, Hideo Momochi. By nature, she is portrayed as friendly and approachable, often interacting warmly with her neighbors and other residents. Like many of the older tenants, she shows a great deal of affection for the young girl Kimi Shirokado and frequently dotes on her.

Her personal life is marked by a strained relationship with her son Hideo, who is a hikikomori—a recluse who rarely leaves their apartment. This tension between mother and son is a subtle aspect of her home life, though she does not outwardly express frustration or anger toward him. Her primary motivation appears to be maintaining a sense of normalcy and community within the housing complex, despite the growing unease among the residents.

Mitsuko's role in the story is brief. She appears primarily in the first episode, interacting with other tenants and participating in the community's daily life. At the end of that episode, she and her son Hideo vanish under mysterious circumstances, with moss reportedly found inside their apartment. Her disappearance is one of the early signs that something sinister is affecting Housing Complex C, contributing to the mounting tension and sense of dread among the remaining characters. She does not appear again in the series after this point, and her fate remains tied to the larger supernatural events that unfold.

There is no detailed backstory provided for Mitsuko beyond her role as Hideo's mother. Her development is minimal, as she exits the narrative early and does not undergo any significant change or arc. She possesses no notable supernatural abilities or special skills; she is presented as an ordinary woman caught in the eerie happenings of the complex. Her primary importance lies in being part of the group of tenants who initially welcome Kimi and later become victims of the mysterious forces at work.