Ryoko was happily married to her husband, and their life together was peaceful. Their sex life was frequent and satisfying. However, she couldn't help but feel slightly unsatisfied with his size. One day, she received news that her husband's son from a previous marriage would be returning home temporarily for exams. Ryoko, who had always treated him like her own son, warmly welcomed his return. When the doorbell rang, she went to the entrance to greet him. Seeing his more mature appearance, both husband and wife felt quietly pleased. That night, she ran into her stepson as he stepped out of the bath, and she couldn't suppress her shock. Through the gap in his towel, she caught sight of his body—so different from her husband's—and in that instant, an unexpected lustful desire stirred within her.