Love You Baby(2004)

Katakura Kippei is in every way a high school playboy. Spending his days flirting with any female 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 fulltime 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. Based on the manga by Maki Youko.