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. Mimio, who had been living alone after losing her husband, was happy to be reunited with Shinji, but Shinji had a strange expression on his face. Apparently, Shinji was hurt both physically and mentally after being dumped by his fiancée. Mio gently hugs Shinji with her sweaty body because she wants to encourage her. However, the moment Shinji's head touches her mother-in-law's chest, she becomes strongly aware of her as a woman...