PLOT:

When 30-year-old Daikichi Kawachi returns home for his grandfather's funeral he learns about the existence of Rin Kaga, his grandfather's illegitimate six-year-old daughter by an unknown mother. The girl is an embarrassment to all his relatives and is treated like an outcast. Annoyed by their attitude, Daikichi decides to take care of Rin himself, even though he is single and has no experience in raising a child. As Rin becomes part of his life, Daikichi experiences the hardships of being a single parent. He is befriended by the single mother , Ykari Nitani, whose son, Kouki Nitani, is a young boy that Rin meets in nursery school, who gives him advice on raising Rin.  

Source: Wikipedia