Uta and her stepbrother live together after her parents remarry. During her rebellious phase, she couldn't stand her stepbrother and was annoyed every time she saw him, but she was also in her teenage years and masturbated in her room every day. Could it be that this masturbation was the cause...? One day, her parents are away for three days, leaving the two siblings alone. Her stepbrother has secretly filmed one of his cheeky sisters having sex, and uses the footage to pressure her into having sex. It's humiliating to have his dick stuck in her, but their chemistry is so good that she climaxes over and over for 72 hours.