Tatsuya lives with his wife and mother-in-law. Though he's moved by his stepmother's gentle side, he finds himself increasingly drawn to her in their daily life. One day, the stepmother purchases an arousal cream. When Tatsuya tries it out, he's amazed by its effects—his nipples become highly sensitive and erect, while her mature pussy overwhelms his senses. Their relationship gradually deepens, giving rise to forbidden feelings. Unable to resist her adorable appearance, he repeatedly creampie her. Lost in pleasure, they make love over and over in the bath, the Japanese-style room, and the bedroom. A lewd and taboo incest story between stepmother and son-in-law unfolds.