when i was about 18, I was staying at my grandmothers apartment, while this might seem odd, she was only about 25 years older than me and she looked good. She made a point of her feeling that nudity was / is normal and she always walked around the place in the nude. I was a bit embarrassed because seeing her naked always gave me a hard on. One morning i woke up in her spare bedroom and began doing what most guys do...I was stroking my cock when she walked in and caught me. Naturally stopped and tried to cover up. But she would have no part of that, she explained that everyone does it and then she put her leg on the bed and began to show me how she satisfied herself when she was alone. I could not watch her without finishing myself off. After I shot one of the biggest loads of my life I watched her rub her clitoris until she came also.
I told her later that I had been jacking off after seeing she walking around the house naked for years. I think that she must have been pleased by this information because, we mutually masturbated together several other times and she actually introduced me to a group of ladies who I had the opportunity to share with later.