妻が隠していたビデオ… ～元カレ寝取らせ観察記～

The protagonist, Honda Kouichi, lives a happy life with his wife, Yuki. Although they have been married for three years and have no children, they spend their days in a close relationship without any signs of a rough patch. Yuki is an ideal wife who's good at cooking, meticulous in taking care of her husband, and proficient in household chores. However, Kouichi has one concern: Yuki doesn't seem to enjoy sex with him. Although they love each other, they don't have sex frequently due to their mutual lack of interest. One day, while walking in the city, they encounter a man who calls Yuki's name. That night, Kouichi becomes curious and checks Yuki's phone, discovering a video of Yuki being trained by a man she met that day. This discovery of Yuki's hidden past causes the gears of their once-happy marriage to begin to malfunction.