Haruki, a wife, felt lonely because her husband was so dedicated to his work that he didn't care about his family, so she started a physical relationship with her brother-in-law Katsumi, and continued this relationship to fill the void in Kokoro. As they continued to meet just once a week, Haruki's feelings of guilt towards her husband gradually changed into love for Katsumi... One day, Katsumi had to go overseas for work. Katsumi, who was serious about his relationship with his sister-in-law, tried to refuse, but Haruki firmly held him back...