Age: 13
Birthdate: January 24
Height: 155 cm
Blood type: B
Likes: ramen
Dislikes: daikon radish sprouts

Natsumi is a first-year middle school student of the Asahigaoka Branch School. She is Yukiko's youngest daughter, and Suguru and Komari's youngest sister. Fun-loving and carefree, she likes playing pranks on other people, talks back to her mother, and does poorly in school. She usually tries to get out of trouble by pinning the blame on someone, or something, else.

She used to have a brother complex when she was younger, promising to marry her older brother, and is very embarrassed of it.