I was 18, and away at school. I was in a rented room and my landlady was a very heavy lady and she had two daughters 16, and 15. In my room was a full length mirror on the back of the door to my room. I assumed that that room had been the girls'. Well, I had always been an exhibitionist, and showed my cock whenever the opportunity presented itself. But alas, away at school I had no chance. However, I would stand naked and look at myself in the mirror, and play with myself, and do various different poses.
One evening I was doing the posing thing, and I thought I heard a noise on the other side of my closed door. I paid no attention and kept jacking off and playing with my balls. The next day, the two girls were giggling. That night I went through my posing thing and played with myself. I heard the same noise again. The next day, I checked my door, and found that one of the panels was loose. I was able to take it off, and there was the two way mirror. The girls were watching me all the time. When I confronted them, they told me that their mother also watched me. After that, I gave them all a fine show.