Kippei Katakura is a 17-year-old playboy who spends his time chasing girls, careless of their feelings. But when his 5-year-old cousin Yuzuyu comes to live with his family after her mother's sudden disappearance, Kippei is put in charge of taking care of her. As Kippei gets to know Yuzuyu and starts to understand how she feels, he also begins to realise that all girls were like Yuzuyu once. . .
Kippei has a lot to figure out, like what to make for Yuzuyu's lunch and how to drop her off at kindergarten while still getting to high school on time. Kippei is enjoying his time with Yuzuyu, but not everyone is happy about it. The girls at school miss their quality time with Kippei, and one decides to play dirty to get him back.
