Hanaotoko

Shigeo is a high strung elementary school student living with his mother. His only concern is getting ahead in life by doing well in school. He despises his father Hanao(who is separated from them), who’s an idealistic free spirit and kid at heart infatuated with the sport of baseball.

Shigeo’s mother forces Shigeo to take time to visit his father and so begins Shigeo’s lessons that there’s more to life than excelling academically (courtesy of his very childish father).

From Mangascreener