After nearly two years of a sexless marriage, Natsuki Aoi decides to seek excitement in her married life. To her home comes Hiroshi, her older sister's son—two years her senior and someone who doted on her since childhood—visiting for the first time in four years. He had stopped by after running errands nearby, seemingly still fond of her. Their long-awaited reunion sparks rising tension between them, and overwhelmed by sudden arousal, Natsuki finds herself irresistibly drawn to Hiroshi's masculine presence. Compelled by deep feminine desire, she gives in to the urge, guiding his hard, erect cock deep inside her. That night, taking advantage of her husband's absence, Natsuki indulges passionately in long-overdue sex with Hiroshi. Unable to restrain their feelings, their rekindled intimacy marks the beginning of a new, forbidden relationship.