Hosaki Mana

Sumire's younger sister a few years later, when she was in high school. After learning as a child that her first love, Masaharu, had become Sumire's boyfriend, she did not lose hope and decided to do everything to become very pretty when she grew up.

Now, she spends most of her time charming Masaharu and telling her sister that men prefer younger girls and that one day she will become his mistress, which bothers Sumire because she doesn't really know if her sister is kidding or not...