Yohei lives a peaceful life with his mother Kaho, and cousin Fumika. One day, Kaho suddenly confesses to Yohei that she is actually not his mother by birth. Although this depresses Yohei, Kaho assures him that he can continue living with her and Fumika, whom he has always treated as a sister, as if nothing has changed. However, a woman claiming to be Ikue, younger sister to Yohei's actual birth mother, moves in next door and asks that Yohei moves in with her. While Yohei is in a state of confusion, the three women attempt to use their voluptuous bodies to seduce him.