Daikichi (Matsuyama Kenichi) learns that his recently deceased grandfather has an illegitimate daughter with an unknown mother. The girl's name is Rin (Ashida Mana) and she is just 6 years old. Everybody in Daikichi's family looks at the girl as an embarrassment and wants no part of her. Daikichi, annoyed by his family's attitude, decides to raise Rin by himself. Even though Daikichi himself has no experience raising a child and is still single. The movie is based on Yumi Unita's popular manga series "Usagi Drop".