Living together in an apartment with his wife and mother-in-law Chiaki, the husband grows increasingly dissatisfied with his emotionally distant spouse. One night, he becomes captivated by his alluring mother-in-law and secretly watches her, eventually masturbating while observing her sensual figure. Noticing his arousal, he forcefully makes her give him a blowjob. The next day, Chiaki is forcibly taken by her son-in-law, but the intense sexual encounter awakens long-suppressed desires within her. From then on, she begins indulging in a passionate affair with him, developing deep emotional and physical feelings, ultimately forming a new romantic bond.