Reika, a married woman, agrees to care for her father-in-law at her husband's request. However, this arrangement is actually part of a scheme designed to facilitate her husband's cuckolding. During caregiving, her father-in-law repeatedly subjects Reika to vulgar sexual harassment—groping her ass, intertwining his tongue with hers during feeding. Though Reika struggles to endure it for her husband's sake, her body gradually falls under her father-in-law's control. As his true intentions become clear, Reika's emotions begin to waver. Ultimately, will she give in and fulfill her father-in-law's desires?