Exhausted of the city and its people, Yuuki returns for the first time in five years from Tokyo to his childhood home in the countryside, on behest of his little sister, Natsumi. For some obscure reason, she remained there alone, and now, to Yuuki's surprise, lives together with their childhood friends. Thus begins his summer break living together with three beautiful sisters, all of whom have not forgotten their time with Yuuki, as well as Natsumi, who is very assertive about her feelings and also strangely eager to give each sister a push.