Yumiko, who is still on good terms with her husband. She was still intimate with her husband. However, recently, her husband's frequency has decreased, and she is feeling frustrated. So, Yumiko starts exercising with a balance ball she received from her son to relieve her frustration. A week later, Yumiko cramps her leg while exercising. Her son rushes over and stretches her leg to fix it. While touching Yumiko's sweaty body, her son feels horny. Yumiko, who is touched by her son, starts to feel strange. Both of them pretend to be calm, but they are starting to become aware…