Fifth-grader Ko Kitamura was born on the same day in the same hospital as his neighbor, Wakaba Tsukishima, who treats him as her boyfriend as a result.[15] One day during summer vacation, she makes him take her to swimming lessons on his bicycle. On the way back, to avoid classmate Osamu Akaishi, who has a crush on Wakaba, Ko joins a sandlot baseball game organized by another classmate, Daiki Nakanishi. Because he has never played before, Ko fields badly, but because he has practiced in the Tsukishima family's batting cages he hits the game-winning home run...