On a record-breaking hot summer day, her son-in-law Shinji, who moved to Tokyo to start working, returns to his hometown for the first time in about three years. Mio, who had been living alone since losing her husband, is happy to be reunited with Shinji, but Shinji looks somewhat gloomy. It seems that Shinji has been hurt both physically and mentally after being dumped by his fiancée. Wanting to encourage Shinji, Mio embraces him tenderly with her sweaty body. However, the moment Shinji's head presses against her mother-in-law's chest, she becomes strongly aware of him as a woman...