Ko Kitamura grows up next door to the four Tsukishima sisters, whose family runs a batting center and café. He is closest to Wakaba, born the same day he was, while her younger sister Aoba, a gifted pitcher, resents how much of Wakaba's attention Ko takes. When Wakaba dies suddenly, Ko and Aoba are left circling each other, bound by her memory and by her wish to see Ko pitch at Koshien, the national high school baseball tournament. School, rivalry and the game keep pulling the two of them back together.