My step-sister is the child of my father's new spouse, a sullen girl with a mischievous, lustful side. She seems aware that I've been peeking at her panties, and I can sense her excitement. When I sneak a look at her changing in the bathroom, she provocatively says, "Wash my back." When my erect cock presses against her firm ass, she twitches and tightly grips it. What starts as washing each other slowly turns into mutual touching, and whenever we're alone at home, she flaunts her panties at me. Unable to hold back any longer, I pounced on her—only for her to willingly respond, staring into my eyes as she gave me a blowjob. Then, she climbed on top and started having sex with me.