Reiko celebrates the birth of her first grandchild by visiting her son and his wife, reuniting with her family after a long time. She enjoys a lively and cheerful conversation with her son and daughter-in-law. That night, the son accidentally sees his mother bathing and becomes aroused. He attempts to make love to his wife, but is rejected once again. Overwhelmed by pent-up desire, he sneaks into his mother's bedroom, quietly pulls back the covers, and begins touching her pussy. As her sex grows wet, he cums hard, shooting his semen all over her pubic hair. Opening her eyes slightly, Reiko watches him leave, wipes away the semen, and begins agonizing over what just happened. The next day, when his wife goes out and he's alone with his mother, he suddenly embraces her tightly and starts roughly fondling her. Though she resists, she's no match for his strength and begins pleasuring him orally and with her hands. Still, she refuses to cross the final line and remains tormented by her son's advances. Late at night, unable to sleep, Reiko secretly begins touching herself. Her heartbeat quickens, driven by a deep craving for fulfillment, and she frantically masturbates. She orgasms repeatedly but her mature body remains unsatisfied. As if reading her mind, her son appears before her. Already aroused and mentally prepared, she can't fully resist him as he thrusts his hard cock deep inside her. Her vagina fills completely, overwhelming her with pleasure, and she instantly reaches climax…