Disclaimer: All participants are at least 18 when these events took place.
***
I looked through the gap of the bathroom door, and saw the same beautiful sight that I had watched for the last week - my beautiful and sexy sister in the shower. Her alluring body was twirling all around, every drop of water bouncing off of her stunning C-cup breasts. I had seen them enough to be able to measure them by just looking. Her light ginger hair framed her slender frame just perfectly, her wet hair sticking and highlighting her smoothly tanned body. She turned around and bent over slightly, revealing her beautiful ass to me. Dropping her shampoo in the shower, she bent down even more, her legs spreading apart slightly to show me what I had been dreaming about. Her pussy was shaved and hairless, and it called to me. I reached for my jeans, undid the belt and let them open. My cock was at its absolute hardest, and I began to rub it up and down. I imagined that she was the one to stroke it up and down, on her knees and looking up and making eye contact the entire time. I closed my eyes as I let the vision guide me further to an amazing orgasm.
I must have closed my eyes longer than I thought, because when I opened them, my sister was looking at me from over her shoulder, a massive grin framing her face. "Hey bro. I see you looking at me. After yesterday's experiment, I think we should do it again." Without hesitation, I grabbed the condom from my pocket and threw off my clothes after locking the door. My sister shut the shower off and kneeled down on the floor. Panicking that we would get discovered, I quickly pulled her away.
"Wait, why'd you switch it off? We're gonna get caught."