Kaoruko's closest friend since middle school. Subaru is noted to be exceptionally pretty by her peers but has a somewhat withdrawn personality, particularly having trouble whilst talking to boys. She's also very protective of Kaoruko, initially disapproving of her relationship with Rintaro and the others before discovering how kindhearted the boys are.

Spoiler

Despite becoming friendly with the Chidori High boys, Subaru feels as though she doesn't fit in with the group despite wanting to be close with them. However, with Kaoruko and the boys' help she reaffirms her friendship with them, even becoming comfortable enough to casually tease Saku and bring him presents for his birthday.