Summer is the most memorable time in the life of the older brother and his sister-in-law Mizuno, as it is a memory and a turning point that completely changes their relationship. That summer, due to the company relocating near the younger brother's house, the older brother asked to stay at his place for a while to settle in and make commuting easier. Here, he unintentionally fell in love with his sister-in-law because she was not only beautiful and skilled in housework, but also deeply understood the psychology of men. Despite knowing that she was his brother's wife, he tried to encourage himself to ignore those thoughts, but she became more and more seductive each day, wearing extremely provocative outfits, even sometimes without a bra. This made him lose control and cross the line with her on a day when the younger brother was not at home. Although he acted wrongly, he knew that his sister-in-law had secretly loved him for a long time, and her love had been given to him since he moved there. Since then, to avoid making the younger brother sad and disappointed, they decided to keep this secret hidden, burying the illicit love affairs they had in their memories.