Kouno Sayuki

The main character's stepmother (his father's second wife) she works as a teacher at a secondary school.

Although she has a strict and serious personality, she cannot hide the fact that she is a woman with a very strong sexual desire. She came to the Kouno family at about the same time as Miwa, but was mostly left alone by her husband.

She is also jealous of Miwa, who is admired by the main character, as she possesses her own wants both sexually and romantically.

She is tormented by the gap between her rationality and the need to be a teacher and a sensible adult.

She is a fan of the main protagonist's novels.