She was widowed eight years ago when her husband, Naoyuki, was killed in a traffic accident in front of their house. She has raised Naomi since then with kindness and a little bit of severity. She is good with handicrafts, and used to knit socks and sweaters for Naomi when she was little; knitting things like stuffed dolls made Naomi happy. Natsumi is a popular teacher at the nursery school, and both children and parents call her "Ms. Natsumi" (夏海先生, Natsumi-Sensei?).