Mamoru was persuaded by his stepmother, Yui, to go shopping with her. In the crowded train, their bodies were pressed tightly together. Every time the car swayed, he became hotter thinking about beautiful Yui. His erect giant penis pierced into Yui's crotch. Thinking she would be angry, Mamoru was surprised when Yui said, 'I haven't done it in a while...' and started stroking his cock. Although he refused due to the risk of being caught on the train, at the next station's restroom, he was raped by Yui. After that, he couldn't forget about her giant penis, and she began to demand it even at home.
