Chika is married to her husband and lives with her father-in-law. Although sex with her husband is bland, Chika is satisfied, but as months and years go by, the number of days and times they have sex decreases. Chika's sexual desire is so strong that her husband's physical strength is at its limit and he gives up. With no choice, Chika masturbates when she is alone to make up for it. Her father-in-law observes her and her married life and keeps a diary to enjoy. At one point, Chika's clothes changed. Her clothes became more revealing, and she was wearing clothes that could be mistaken for no bra or no underwear. At first, he thought it was part of her sex with her son, but when he looked back at the diary, he noticed that she had been dressing like that since the sex with her son had decreased and stopped. One day, her husband went to work and her father-in-law went out on an errand, and while she was enjoying her time masturbating alone, her father-in-law, who had been stood up, returned. Her father-in-law looked at her in shock as she was masturbating, but he was excited by her painful moans and took her under his control. Her father-in-law's experienced caresses were intense, and her persistent cunnilingus made her cum over and over again. Her father-in-law's penis was bigger and harder than her husband's, and she climaxed the moment he penetrated her. A few days later, when her family was out and she was alone, she stumbled out and took her father-in-law's underwear out of the laundry basket and gently sniffed it. Remembering her act with her father-in-law, she ran her fingers down to her crotch, and found that her underwear was obscenely damp...