When I was growing up we often would go to my aunt's parents house as they owned a pool and we would learn to swim. During one summer my aunt's 5 year old neice was visiting with her 7 year old brother. I was 8 at the time and had never seen a naked girl before.
Everyone would change together so I was used to being naked with my cousins and other guys. We were encouraged to swim nude if we wanted to (but out of modesty and fear of what my parents would think I never did)
My aunt got her neice ready to swim in front of us that day. Before putting on her water-wings (she couldn't swim) the girl (who I'll call Karen) was undressed by my aunt for swimming.
I screamed, 'you broke her penis off, where is it?' not knowing little girls didn't have penises like us boys. My aunt laughed and said that girls don't have penises and that they have vaginas and one day I would know the reason why.
I asked if it was okay to touch Karen's vagina to know what it was like. My aunt hestitated and then said it was alright as a one time learning experience. I remember it feeling very warm to the touch.
After swimming was over we usually changed into our clothes or lounged around playing in the buff. Karen was allowed to do this too.
This is when I noticed her rubbing her pussy up against furniture and putting her fingers inside of herself.
There was nothing sexual about it as she was just doing it watching TV or when she was bored. She was very gentle about it and never pounded at herself. It was kind of like a beautiful thing in a sense.
I told my aunt about this and she said girls do that and that's all that was said about it. Later on years later I learned about masturbation and discovered what the beautiful thing was that she was doing.
I've since seen many girls masturbate but none was as good as that first time seeing it.