Hinata Mayuri

The girl next door (23 years old) who has loved the main character as if he were her little brother. She is serious and kind, and the protagonist has always admired her.

After graduating from college, she marries the protagonist's father and becomes his stepmother. However, their relationship is the same as before, and they treat each other like a sister and brother.

She is a little careless, so when she runs into him in the hallway wearing a negligee, she gets a thrill. He doesn't seem to mind it too much, but it seems to make the protagonist a bit uneasy.