Husband Kazuhiro returns to his hometown with his wife Mayu for her delivery. Reuniting after a long time with his sister-in-law, Meguri, he becomes aroused by her sensual behavior, sparked by the pregnancy and their reunion. Unable to sleep late into the night, he finds himself drawn to her allure. One night, he accidentally discovers her masturbating. The next morning, haunted by the image, Kazuhiro grows restless and tormented. Noticing his state, Meguri—her own daily frustrations mounting—can no longer suppress her urges and instinctively devours Kazuhiro's cock.