After the passing of his mother, Keita Suminoe's life completely changes when his father remarries. He gains two step-sisters, Ako and Riko, who immediately become attracted to him causing their sibling rivalry to take a bizarre turn. As Keita nears the end of middle school, he is consumed with confusion over his taboo feelings for his sisters. This is further complicated by the advances of other women clamoring for his attention, making it hard for him to resist temptation. In his dedication to attend the same high school as his sisters, Keita must confront his overwhelming inner conflict, which puts everything to the test.