Beautiful sisters Eriko and Miki appear together. Miki is having an affair with her real son Wataru, and to deepen their relationship, she involves Kiyotaka—the son of Eriko—into a four-person encounter. One day, Miki uses her voluptuous body to seduce Kiyotaka, while Wataru assaults Eriko. The result is an unprecedented mother-son swap, leading to a bold and intense incestuous scenario.