This happened when I was 16. Across the street from me lived this incredibly hot girl named Sarah. She was one year younger than me and good friends with my little sister. Our rooms faced each other on the street. Often I would get changed out of my clothes with my blinds open, not thinking anyone could see in or would want to. I was wrong. One day my sister told me that Sarah liked my cock. I was shocked to learn this and wondered how she could have seen it. My sister told me that she and her friends were talking about sex one day and someone asked if anyone had ever seen a penis. The only one who had was Sarah and it happened to be mine. Apparently she would always watch me undress and had seen my cock on a few occasions. And she liked what she saw.
This really got me excited knowing that she had seen me naked. So one night I went to my room to go to sleep. My blinds wee open and I went to shut them, when I thought about Sarah possibly watching me. The light was on in her room, so I decided to leave the blinds open. I undressed and just lay on my bed naked.
The thought of this hottie watching me was turning me on. Slowly my cock started to swell and soon I had a very hard erection. Being a horny teenager I was all for doing something about it. I started to play with the head of my cock between my thumb an forefinger, gently twisting it. Then I wrapped my hand around my shaft and began to pump. I stroked and stroked, never looking to see if Sarah was watching because I didn't want to startle her in case she was. Soon it was all over. I felt that incredible release as my hot sperm erupted from my cock all over my stomach. I cleaned up, shut the blinds and went to sleep.
I still don't know if she ever saw that. I never had the courage to do it again and even started making sure the blinds were shut when I undressed, worried someone unwanted might see me. But the excitement of that one time and just knowing she may have seen it is something I'll always remember.