Kanna, a former secretary to a company president, married a businessman despite their age difference. Although she is his stepmother, as a mother she worries about her son who stays at home even though he is an adult, and takes good care of him. One day, to cheer him up, the stepmother gives him a massage. However, as she massages him, his penis starts to grow bigger and harder, and although she is confused by his bulging penis, she unconsciously gets wet. Her excited son begs her to give him a handjob...!