Nanase Matsuri

Ayumu and Rikuto’s friend and classmate. She has been Rikuto's "ally" since they were in middle school. The reason that Matsuri and her mom don't get along is that the mom's got maternity neurosis. Rikuto then founds out that she is missing ovaries and is unable to ever have children. A bit of time later, Rikuto takes her to the nurse's office, and then, it turns out her period started.