This was my first time and I just got very lucky, just follow your instincts and good things happen.
I was 14 and lived in a regular suburban neighbourhood, maybe slightly more rural than regular. I was about 5'8 and 130 lbs., I was muscular, but not a muscle head and my 'manhood' parts had grown in quite nicely to about 6 inches then. I lived just out of walking distance of everything in our town, so I spent a lot of time with my neighbors. She was the only mature one in the neighbourhood as of everyone was either 18+ or less than 11, so I would talk to her a lot about things, we both had our girlfriends/boyfriends, but we both only got to making out, not feeling each other. I had masturbated before, usually 5 times a week or so, but I kept that to myself. She was 15 and had always seemed attractive to me, she was about 5'5' and 110 lbs. but I had kept myself in control, I had much experience being around friends who had hot bodies. I always thought she had the best boobs out of any girl I had seen in person.
This night no one felt like doing much, so we sat and talked. Later that night her parents went to a concert and wouldn't be back until 11:30. So we were sitting on her couch in the garage just talking. I had a little fairytale book in my hand, sleeping beauty(I never forgot that book for its purpose in this), it was one of her baby brothers. She took it right from my hands, and I being a very competitive athletic guy went to get it back and this ended up in a 'wrestling match' over the book.
I had lost grip of the book and got a nice feel of her boobs, then I started to get a sexual desire out of this rather then a book, I think she did to from the way she looked at me.
We then started to 'accidentally' lose grip of the book ending up with me squeezing her boobs/feeling her butt or she falling on me/feeling my butt. One particular time I had pulled her down right on top of me and I got a good feel of her with my penis. This combined with her low cut shirt falling down leaving her boobs completely exposed, I was getting hard. I had a hard on in about 30 seconds and there was a tent already forming. We had sat back a second and my tent around my crotch was very noticeable and she definitely saw and was staring at it.
She was fascinated by it, and I getting redder by the second I made no effort to cover it up as she had already saw it and it would only make it more embarrassing, she took it in between her forefinger and thumb squeezed it and asked 'did I do that?' and I answered 'yep'. she asked what I was hoping so badly she would ask, 'can I see it?' she asked, I undid my belt and unzipped my pants and exposed my now rock hard boner. She gasped and without saying a word started feeling it. When she was done she said how big and hard it felt and I told her she had done that. I told her to keep on rubbing it and it felt good. I took her hand and rubbed it up and down and told her to keep doing that. I started to feel her boobs and moved my way down to her inner thigh and I told her I wasn't gonna last long with her skin. About a minute later I could feel it coming and started moaning and I told her I was gonna come. I cummed the most I had ever before, it went all over her hands, my shirt, chin and even one landed on my ear in about 10 long ropes.
She was still very fascinated when I cummed and she said she had never seen anything like it.
We continued talking about it until we saw headlights heading up the driveway. We were busted! but she quickly told me to hide behind some plant pots and I laid down on the floor still open and exposed. She talked to her parents and told them she was looking at the stars and they went in. I quickly got up, zipped up and said my goodbyes and I left.
That next day I went outside with my neighbors we went to sit on that couch, lucky I got there first for there were two stray now dry cum puddles which I quickly hid.
We did this about once a month, after that first time I started masturbating her too, until she went off to college and I haven't heard from her since. maybe I can still reach her through her parents. even if I don't I will always remember her and my first time masturbating with a girl.