Sayama Makoto and Agari Yamato's friend and classmate.
Matsumoto Kiyose is a smart and quiet bookworm who is often found with Oume Hibari, Otake Akitsu, and Sayama Makoto. She is also the oldest of the group, followed by Sayama. She gets nervous easily. She has been friends with the three girls for an unspecified amount of time, and friends with Kodaira Rune and Agari Yamato since they were 10 years old.
As a child, she once used her status as student librarian to sneak her favorite manga into the class bookshelves. She was later found out by Rune and Yamato, who forgave her.