While his wife was visiting her hometown, her sister Konatsu came to check on him. They were happy to have a guest for the first time in a long time and were chatting away, but the situation changed when Koji got into the bath. "Sister-in-law, please don't come in!" Konatsu insisted on washing his back, but he gave in and the two of them ended up in the bath. Seeing Konatsu's defenseless and beautiful body in front of him, his desire began to rise up within him, even though he knew it was wrong.