Katakura Kippei is in every way a high school playboy. Spending his days flirting with any girl he can see, responsibility is the last thing on his mind. Life takes an unexpected turn for him as one day he returns home to find himself with the full-time task of caring for his 5-year-old cousin. Kippei's aunt Miyako had disappeared, appearing to have abandoned his cousin, Yuzuyu. With Kippei's lack of responsibility and knowledge of childcare and Yuzuyu's injured heart with the disappearance of her mother, their time together is in for a bumpy ride.