This happened one summer vacation when I was 11 or 12 with my sister who is a couple of years older.
It had been a very long, boring summer for us as a lot of the kids in our neighborhood had moved away or were at camp. So, this left me and my sister with a lot of time by ourselves. We had played 'doctor' when we were younger but had not done done anything like that for sometime. One particularly hot day we decided to turn on the sprinkler to cool off. When we were finished, we went in to change. I changed very quickly and went in to her room, where she had not gotten dressed yet. She tried to cover up with a towel but dropped it so I got a very good look at her naked body. She was probably 13 or 14 at the time and had obviously started puberty. Her breasts were very full-I'd say a large B-cup-and she had a lot of very red hair on her pubic area. I had never seen a naked girl before and was very aroused by the site of her naked body.
Anyway, she did manage do get herself covered up and ask if I had seen anything. She had to have known I did. I said yes. She asked what I saw. I said your boobs and hair. She then asked me if I had any pubic hair yet. I told her I did although it was not very much. She then suggested that since I'd seen hers, she wanted to see mine. I found this to be very arousing and felt my penis become very erect very quickly. I said ok but that I had a hard on. She looked surprised by this, and then asked if I knew what masturbation was. At this age I did know how to do it but didn't know what it was called so I said no. She let her towel drop and told me to get undressed, which I did. My little dick was pointing straight up.
As she stood there looking at me, she started to play with her pubes and ask me if I wanted to touch her. I quickly said yes and we both sat on the floor in front of each other. She had her legs crossed and her lips were slightly apart. She put her finger down to spread them more and started pointing out all the parts. She showed me her inner lips, clit, and vagina. She then asked if I wanted to touch them and I immediately told her yes so she took my hand and let me explore her with my finger. I immediately wanted to put a finger in her vagina, which I did and she told me that it felt nice and to move it in and out of her. As I did this she started to finger her clit in a circular motion. I continued to finger her and she told me to do it faster. This went on for some time and then she started to rub and gyrate her hips until she came.
After she had cum she told me it was my turn. She told me to grab my penis in my hand and to stroke it. As I did this she played with my balls and told me to lie back. I was stroking myself so hard and fast I was soon cumming. I had had orgasms before but this was the first time fluid came out. It was the best cum ever.
As the summer went on we masturbated with each other quite often. It was a lot of fun.