Living together with her son-in-law in an apartment, stepmother Ryoko was left sexually unfulfilled due to her husband's emotional and physical coldness, causing her to seek satisfaction elsewhere. One night, her son-in-law becomes intrigued by Ryoko's alluring appearance and accidentally sees her in a seductive state, leading her to forcefully make him perform a blowjob. Experiencing pleasure unlike anything before, Ryoko awakens to new sensations that night and gradually grows interested in her son-in-law. From then on, the two indulge in intense sex, and deep within her heart, a new emotion begins to bloom.