Last winter, Shota's father remarried. His new wife is the beautiful and busty Rika. Shota had a hard time getting along with his stepmother, but one day, a friend of his envied him for how beautiful his mother was and how her breasts were amazing, and Shota's outlook on Rika gradually began to change. He ended up masturbating to a photo of Rika. Later, Rika and Shota washed each other in the bath. And then his penis got bigger... He even showed up in Rika's bed, begging her to do it again. Shota can't stop himself now, so he hides from his father and plays naughty pranks as much as he wants.