My clear-headed sister-in-law suddenly becomes erotic one day. Akiho, who married my brother, treats me, a hopeless NEET, kindly. My feelings for her turn into love, and I even spy on their married life. Then Akiho changes her attitude towards me... My sister-in-law secretly straddles me in a riding position. Intimate sex next to my sleeping father. Showing off her pussy and indulging in masturbation... And our relationship... A story of intense intimacy unfolding under one roof.