Due to my father's remarriage, I suddenly gained a stepsister, and we began living together. From the start, she showed no restraint—flashing her panties beneath her short skirts, letting me catch glimpses as I stared. When she noticed me watching, she'd tease me by wiggling her tight, perky ass close to my face, and my heart would race every single day. Whenever the rest of the family went out, we were left alone together, and she started asking me to give her massages. As I kneaded her big, round ass, she grew increasingly aroused, until before long, my cock was rock hard and clearly visible through my pants. Even though she acted tsundere at first, she eventually began teaching me all sorts of dirty things, and I responded with relentless, pounding thrusts from my energetic teenage cock, making her cum over and over again in endless ecstasy.