When Keita Suminoe's father remarried, not only did he gain a new mother, but elder twin sisters as well. Distinct yet similar, the homely and mature Ako is a former student council president, while the athletic and aloof Riko is the previous disciplinary president. The three of them have been together since kindergarten, resulting in a deep bond between the siblings. However, over time, their relationship developed into something more romantic—and erotic. Now in his last year of middle school, Keita has already received a sports recommendation, but it's from a different high school than his two sisters.