I was kind of late to hit puberty. So my slightly younger sister turned out to have a head start on me and knew things I had no idea about. For several years we had been playing a game. We would pose nude for each other but the other person had to be looking through the keyhole. The one watching would tell the other what to do, what position to be in and so on. Jane actually got pretty good at drawing me nude. I tried drawing her but never got good at drawing much of anything, though I really did try. One night I started having wet dreams and would have one each couple of nights. I hadn't learned anything about masturbation and don't recall even having heard the word.
Shortly after the wet dreams started Jane wanted me to pose for her. So I did, and set up my chair in front of the door and aimed the lights to give good lighting. Shortly after settling down into the pose as Jane directed through the door something happened, my normally flaccid penis got hard and stiff and somehow felt different. I guess I hadn't been paying much attention because I hadn't noticed how much it had grown in the previous year. Jane giggled a bit and said 'What's happening?' I said that I didn't know, that for some reason it just started sticking up for no reason at all. She had me change position so that she had a different angle on it and to move up closer to the door and adjust the height of my seat. I ended up sitting on the unabridged dictionary to be at the right height. I sat there holding the pose and my penis got stiffer and stiffer and started leaking some really slick drops. They started dripping all over. I was going to get up and get some tissues when Jane suggested that I just rub the drops around so they wouldn't drip down.
That worked. So as I sat there I just started spreading the drops around with my fingers. It felt good. I didn't really think anything about it at the time. As I spread them around the leakage rate increased requiring that I spread them out farther down the shaft instead of just around the head. I noticed that instead of hanging down my balls were being pulled up. I pointed out this change to Jane by gripping my penis with more of my hand and pulling my penis up out of the way so she could see my balls better. All she said was 'Neat'. Then she added 'Keep holding it up so I can watch them. They are squirming around in an interesting way'. The warmth of my hand around my very slippery penis felt good but made it difficult to keep my penis up out of the way as my hand kept slipping. My hand kept slipping up my penis so I kept moving it down again and my hand kept slipping up the shaft again. It felt really good and so I just kept on doing it. After a while I noticed that my breathing was faster and that my penis was starting to feel full in a different way. Suddenly it felt very warm and almost like I was going to pee and my penis started throbbing and all this white stuff started spurting out. Jane said 'WOW' and nothing else. After that it slowly deflated back to a much smaller size.