One day, a high school boy, Ninomiya Shungo, is ordered by Ryoko, his elder sister, to live with a beautiful girl, Tsukimura Mayu, in the same house together to cure her androphobia. As a cure for androphobia, they force Shungo to do various things like taking a bath together, or sleeping on the same bed. After Hojo Reika moves in to keep an eye on this "training" between Mayu and Shungo, the house has become quite lively. But is this seemingly random situation between Shungo and the two girls truly an accident or is there more to it...