One morning, her son's erection was unusually huge, causing him to put his pants on inside out. Mother Rumi Ko reached out to help, but his cock was already throbbing with prominent veins. The boy said it usually didn't subside until nightfall. Since he knew nothing about masturbation, Rumi decided to teach him a way to calm himself down on his own. Gripping his already wildly erect penis tight from early morning, she began to guide him.