To be completely honest I didn't discover masturbation until I was fifteen. I had touched myself before and purposefully tried to get hard but it had never occured to me to try jacking off because it had never been fully explained to me (most likely to keep me from doing it.)
I don't remember specific dates but I remember it happened in late November and where I live is particularly cold towards the end of December. I was alone most the day and as a result decided it was finally the time to figure out how masturbation worked. I went up to our loft room and sat on the couch and just unzipped my pants and reached into my boxers to bring it out. I started just stroking it and fondling it and in no time I was hard.
At this point two things happened. First was a tingling sensation that went through my whole body and I was suddenly feeling hot and I could feel the blood coursing through me. My body urged me on to keep touching myself, to keep stroking my penis. The second thing that happened was my dad came home. I quickly turned the TV on and pretended to be watching it while my hand was working furiously on myself. Luckily the couch faces away from our kitchen or else he would've seen what I was up to. It was late in the afternoon and he had his laptop from work set up on the kitchen counter as he did some work. I tried to be quiet because I could hear my nuts smacking against my hand so odds are he probably could to.
He started talking to me asking how my day was and the usual nonsense parents ask and I barely managed to respond to them as this wonderful feeling started to build up in me. My cock was aching and so hard by this point and I couldn't stop. Quite suddenly at about the same time that my dad asked me if I wanted to go out to dinner since my sister and mom weren't home I came. The feeling was a shock to my system as the most incredible feeling raced through my body. I managed a grunt but it was more of a grunt to acknowledge the great feeling rather than going out to dinner.
As I went to pull my boxers and pants back over myself I noticed I had gotten jizz on my pants and there was nothing I could do to clean myself up before dinner. Luckily my jeans were dark so he couldn't tell.