I lived in an apartment building that was across from another apartment building, and my windows gave me a great view of a guy in the other building a floor below me. I watched him in the bathroom and bedroom without him ever knowing. I saw him jerk off many times, have sex, etc. When Has Anyone Caught Someone Jerking And Secretly Watched Them?
I first saw him on the street, I said hello and tried to start a conversation. He was aloof and cold. I wanted to tell him what I've been watching but I thought what the hell, as long as he gave me a free show who needed his friendship. It went on for more than a year.