On a midsummer day with record-breaking heat, Shinji, the son-in-law who has moved to Tokyo after joining the workforce, returns to his parents' home for the first time in about three years. Mio, who had been living alone after losing her husband, was happy to be reunited with Shinji, but Shinji had a somewhat uneasy expression on his face. Apparently, Shinji was hurt both physically and mentally after being dumped by his fiancée. Wanting to encourage Shinji, Mio gently embraces him with her sweaty body. However, the moment Shinji's head came into close contact with his mother-in-law's chest, he became acutely aware of himself as a woman...