Kou Kitamura is a fifth grader whose family runs a sporting goods store. One of the regular customers of his family's store is the Tsukishima Batting Center, and so he gets to know the four daughters of the Tsukishima family (Ichiyo, Wakaba, Aoba, and Momiji) very well. Since Kou has spent so much time practicing in their batting cages, he has become a genius hitter, but has no knowledge of any other aspect of baseball. This is in contrast to Aoba, who, despite being a year younger, is an adept pitcher and hitter. Wakaba is a classmate of Kou's, and she seems fully intent on marrying him when she grows up. All seems idyllic in their world, until tragedy strikes. The story then skips ahead to four years later, as Kou has continued the training he began four years ago, but has not played in a baseball game since. As he finally begins playing again, it remains to be seen whether or not he will live up to the expectations of those who know the true talent he has been hiding all this time.