(I did it...) Yoshinori has betrayed his wife. The reason for this is his sister-in-law, Yuu, who is right in front of him. His wife goes on a two-day trip, and Yoshinori is enjoying the freedom of living alone for the first time in a long while. Then, suddenly, Yuu comes to visit. In truth, Yuu has come to Yoshinori to relieve her sexual frustrations... but Yoshinori had no idea about this and invited her in. Yoshinori feels at ease with Yuu, who helps with the housework, and when he goes to take a bath, Yuu comes in too...