Risa raised her son Keisuke on her own, and when he entered university, she married a man who also had a son. Three years have passed, and Risa has been servicing her husband's cock and her stepson's mouth daily. However, Keisuke suddenly returns home after securing a job at a local company. While Risa is relieved that she and her son can live peacefully, her husband and stepson have other plans. They force her to offer her new hole—her asshole—to Keisuke. The bond between mother and son now faces a new trial.