Kiyotaka is tormented by the experience of swapping with his mother, Eriko, his aunt, and even his cousin. Eriko tells her son to forget about it, but Kiyotaka cannot forget the sight of his mother drowning in pleasure, and is overcome by a forbidden urge. Then, with her son's restraints now out of control, Eriko becomes addicted to forbidden pleasure, desperately trying to hold back her voice right next to her husband...