My stepsister has big boobs. However, she's unaware of this and wanders around the house completely defenseless and braless... Honestly, every time I see her like that, I get a rock-hard erection. This means that when she's at home, I'm practically rock-hard, which is an unusual situation. And because she sees my bulging lower body every day, she mistakenly assumes I have a huge penis. And even though my penis is actually average-sized, she asks me, "It's big, isn't it?", clearly showing her curiosity about it! Was this my chance? I had ulterior motives: I wanted to fondle my stepsister's big boobs, so I didn't want to miss this opportunity! I was ready to cross the line! Since I was fully erect, my penis was huge! We were both tantalizing each other every day, and we just couldn't stop! We just kept fucking and cumming! Our relationship started with a misunderstanding, but honestly, it wasn't so bad.