30-year-old bachelor businessman Daikichi Kawachi encounters Rin, a girl he's never seen before, at his grandfather's funeral. Surprisingly, the 6-year-old girl turns out to be his grandfather's love child. Daikichi doesn't like children, but the cold attitude of his relatives towards Rin makes him uncomfortable. And then, the relatives' meeting to decide who will have custody of Rin begins at last...

What kind of clothes to buy her? What to feed her? What to do about nursery school? Daikichi's new life raising a 6-year-old girl is an uninterrupted stream of bewilderment. Rin looks anxious on her first day of nursery school, so Daikichi does a "pinky swear" with her, promising to pick her up as soon as he can. And Daikichi, who has no confidence he can live with Rin for long, starts thinking about meeting Rin's mother...