After the death of his mother, Shichimi sets out to join his half-brothers and -sister who live together in Karakuri Tenement, a place provided by the father they have never met.[2] He finds out that each of them had different mothers (all of whom have died), but were fathered by the same man. Not long after Shichimi's arrival, the siblings decide to journey to visit the graves of each of their mothers. On this journey, they encounter many dangers.

From: Wikipedia

Satoyama Katsuki is a carefree 15 year-old high school kid, and a pretty lazy one at that. However, he secretly has a crush on a girl who happens to share his name: Mizutani Katsuki. Upon finding out that Mizutani's father used to be a pro-boxer, and she herself infatuated with the sport, he reluctantly joins a boxing gym in order to impress Mizutani. Satoyama is quick to find out he may have the blood of a genius boxer running through his veins...

Minori is the manager of her high school's baseball club, which has been defunct up until five years ago. Even now, it's a little rough, since there currently are no seniors in the club at all! None of the second year players know why the club closed so many years ago, or about the baseball history all their fathers share...
(Source: MangaHelpers)