An is a smart woman who used to be a secretary to a company president and remarried a man who runs a company. Even though she is a stepmother, she is concerned about her son who stays at home even though he is an adult, and takes good care of him. One day, An gives her son a massage to cheer him up. However, as she massages him, his penis starts to grow bigger and harder, and although An is confused by his bulging penis, she unconsciously gets wet. Her excited son begs her to give him a handjob...!