Nao is married and lives with her husband and his father. Her sex life with her husband had been routine, but she was reasonably satisfied. However, as one month, then one year passed, the frequency and number of times they had sex gradually decreased, until it eventually stopped altogether. Nao has a strong sex drive, but her husband's stamina had its limits, and he would finish quickly, clearly exhausted. With no choice, Nao began satisfying herself through masturbation during her alone time. Her father-in-law quietly observed this marital situation every day, secretly writing about it in his diary and enjoying it immensely. At some point, Nao's clothing began to change—becoming increasingly revealing, often going braless or even without panties. At first, the father-in-law assumed this was part of her relationship with his son, but upon rereading his diary, he realized these changes coincided with the sharp decline—and eventual end—of her sexual activity with her husband. One day, her husband went to work and the father-in-law claimed to have an errand. Left alone, Nao began pleasuring herself—only for the father-in-law, who had actually returned early, to walk in on her. Seeing Nao lost in ecstasy, he was initially shocked, but quickly became aroused by her desperate moans and took her for himself. His experienced, skillful touch overwhelmed her, and she was brought to climax repeatedly by his relentless, thorough cunnilingus. His cock was larger and harder than her husband's, and as he thrust into her deeply, Nao reached a powerful, undeniable orgasm. A few days later, with the family away, Nao found herself alone again. She wandered over to the laundry basket, pulled out her father-in-law's underwear, and softly inhaled its scent. As memories of him flooded her mind, her fingers drifted to her pussy—only to find her own panties soaked and dripping with arousal.