Once, when I was fifteen, I jerked off into a girlie magazine in the toilet at work; I found it on top of the cistern, so I grabbed it.
It wasn't a very good one, but it had pictures of scantily clad women. They were mostly just topless, just wearing panties or a bikini bottom, and the few that were naked didn't even show pubic hair.
I dropped my pants and sat, and had a look at it anyway. There were some good pictures in there, and soon I had an erection, and I started masturbating.
I really liked one of the girls; she was a rather slim young thing with small breasts, and she looked about sixteen.
She was wet like she'd been swimming, and was thrusting her hips towards the camera; her pants were wet, and when I looked closely I could see the shape of her cunt.
I got really excited and started jerking faster; then I shifted forward to the edge of the seat and lowered the book so that I could see her tits and my cock at the same time.
By then I was seriously wanking and I put the tip of my cock against her nipple and massaged my cock at the same time; it felt cool on my knob, and it looked really good. She had a cheeky grin on her face, and a lovely little body, and I could see the shape of her cunt.
I lowered the book again and put my cock up to her mouth; and if I held it in the right place it looked as though she was sucking it. There was a little drop of come on the end of my cock and it left a mark on the picture.
I was getting close. I put my cock against her pants this time, trying to imagine what it would feel like in real life. It looked fantastic and suddenly, I knew I was going to come.
I jerked it frantically, holding the book under my cock; then I started to come, and I watched as my semen rushed out on to the picture. I had never done this before and it felt dirty; but It looked good; and it looked like I was really coming on her.
I made sure it went on her pants, and her belly, and her tits, everywhere. I even smeared it on her face with the tip of my cock. It was exciting and I massaged it for as long as I could, squeezing the last drop of come on her body.
When it was over there was a come all over the picture, and I looked at it, marveling at what little things excited me; I had just jerked off into a magazine and I was pleased with myself.
I closed the book and put it back where I found it, knowing that someone would find it; and know what I'd done. It's interesting how much the little things add to the satisfaction; like jerking off while there's someone in the next stall, or coming on the floor and leaving it there.
I went back two days later and the book was still there; when I opened it I had expected the pages to be stuck together, but they weren't. They were stained and yellowed, and several pages either side; and they were sort of stiff and wavy, but dry.
I wondered whether anyone else had seen it, and what he had thought. Someone must have seen it; after all, someone had put it there in the first place. He must have jerked off over it as well.
The thought of that made my cock stiff and I jerked off again, thumbing awkwardly through the same magazine. This time I leaned forwards and pointed my cock down in to the toilet, and came directly into the bowl.