I grew up next to a house that had been empty for years. While I was growing up I was always curious about what it was like but I was never allowed to go in until one day I decided to go and take a look.
I crawled through a gap in the fence and explored around the yard a bit. Since there were high hedges all around the land nobody could see in but it was right next to a main road so there was traffic and sounds of people filtering through. I felt as though I could be caught trespassing any minute.
Since I was almost a teenager I randomly became aroused while wandering around the house and, since nobody could see me, I decided to try something new. I stripped completely naked and, leaving my clothes in a pile by the gap in the fence, I explored the yard completely naked. The feeling of freedom was exhilarating. I was getting hornier by the minute and I slid my foreskin back so that I felt the cool breeze on the head of my penis.
By now I was around the front of the house so I sat on the porch steps and looked at my rock-hard cock, I wasn't fully grown yet so it was around 4 or 5 inches in length and about 2 inches wide with a mass of bushy pubic hair at the base. I'd played with myself before but never to completion so I decided I'd see what happened if I kept going. I slowly stroked the length of my shaft and closed my eyes engrossed in the ecstasy of the moment. With my other hand I started to play with my balls and imagine being sucked by one of the boys in my class at the time.
I started to feel like I needed to pee but since I was outside I kept going figuring I could just pee on the ground and I imagined what it would be like to be caught being so naughty. Just at that moment I heard a small gasp and opened my eyes... My sister was standing in front of me staring at me with a look of complete shock on her face.
I stood up suddenly and was about to shout at her to leave but it was too late. I'd gone too far. My whole body shook and I let out a small yelp as my first orgasm hit me. Thick ropes of cum shot out of my cock and landed on the ground between us. I actually had to hold on to the house for support as my knees buckled and I stood there gasping for about a minute until I felt steady enough to stand on my own. The feeling was the most incredible I've ever experienced. I opened my eyes and my sister was still staring at me, her eyes even wider than before.
She realized the show was over and must have felt compelled to say something. She cleared her throat and said, 'Wow. Well...errm.. You'd better clean up, dinner's ready' and then she turned and headed back to the fence.
As I headed back to my clothes I was dreading what she would say to our parents but throughout dinner she just looked at me with a strange smile on her face. Since then I've masturbated many times to the memory but we never repeated the experience.