I am currently living on campus on the 13th floor and this happened to me about 3 weeks ago. I never thought this would happen to me but it finally did.
I had a friend on the same floor as me and all though we had talked about sex and girls, we never really talked about masturbation, other than the occasional joke now and then. The showers were separate so I had never seen him naked before and never really tried.
One day I was walking by his place and he had his music turned up real loud like he usually does so I knocked on his door to see if he had anyone over. No answer, so assuming that he couldn't hear me because of the music I walked in. Now at 8:00 in the evening, I would assume that he wouldn't be changing, and if he was he would have locked his door, but to my surprise he was sprawled out in the middle of his floor, dick in hand and with his eyes closed.
I shut the door quickly, and interpreted what I had just seen. He couldn’t have seen or heard me, he would have jumped up, so I opened the door again and sure enough he was still going at it. I walked in and closed the door behind me, this time locking it, and then sat down on his bed watching with anticipation as to what was destined to happen. Then all of a sudden the cd started to skip, he jumped up to turn it off and noticed me just sitting there. He then turned off the music and started apologizing profusely. I simply said its cool man, I do it all the time, every guy our age does.
He looked at me again but then got a grin on his face, he said well it would only be fair if he saw my dick since I had now seen his. Now normally I would decline, if it weren’t for the tent I was sporting in my jeans which was not going anywhere soon, so I said sure. I unzipped my jeans and released my peter, it flung into action twitching with excitement as it met the cold air. He then walked over to me and began to stroke it. Overwhelmed with pleasure I feel into the mercy of his hand, and I reached over and began to stroke his dick slowly, I couldn’t believe how good it felt and how hard and warm his cock felt in my hand. He was having trouble standing as he shuddered with pleasure, and I told him to sit down, so he did and we began to stroke faster.
The next thing I knew he jumped up again and aimed his dick right at my crotch as his cum spewed out in multiple ropes of warm ecstasy, putting me over the edge as I erupted in bliss. We cleaned ourselves up and have done 3 times since then.