Summer is the most memorable time in the life of the older brother and his sister-in-law Mizuno because it marks a moment that completely changes their relationship. That summer, due to the company's relocation to a location near his younger brother's house, the older brother decided to stay at his brother's place for a while to settle in and for convenience in commuting. Here, he accidentally fell in love with his sister-in-law because she was not only beautiful and skilled at housework but also very understanding of men's psychology. Although he knew she was his brother's wife, he always tried to encourage himself to push those thoughts aside, but over time, she increasingly acted seductively in front of him by wearing very revealing outfits, sometimes without even wearing a bra. This drove him to lose control of himself and he crossed the line with her on the day his younger brother was not home. Although he was the one who acted wrongly at first, he knew that his sister-in-law had secretly loved him for a long time; her love had been given to him ever since he moved here. Since then, not wanting to make the younger brother sad and disappointed, the two decided to keep this secret, burying the clandestine affairs they had caused only in memory.