This happened at college a few months ago.
We were friends, but we weren't close. We spoke every once in a while, sat next to each other in one of our classes but that's about it. We also followed each other's postings online. Mine are very clean, whereas hers are much more personal and, in a word, dirty. I kind of got turned on reading them, I guess I found it hot that my friend could be so naughty and say such things, it was like "oh xxxxx I wanna have your babies", "my search engine just blocked the word porn, my evening's ruined" and "is it okay to masturbate in a movie theatre if the guy's really fit?" I'm open about my masturbation habits and it was good to see she was too. I replied to that posting: "as long as you don't get caught!" I felt a little frisky after sending that, so I masturbated to the idea of her masturbating.
The next day in college she saw me in the cafeteria and asked if she could speak to me. I said sure, and followed her to a quieter part of the cafeteria where we sat down alone. "What did you mean by your reply to me yesterday?" "Nothing, it was a joke. Why?" "Well, did you WANT me to masturbate in the movie theatre? Were you encouraging me to?" "No, why would I do that?" "I don't know, it just seems weird you would reply to that particular posting, you could have chosen loads of others." "Well why does it matter? You're obviously open about the fact you do it, why can't we joke about it? I do it too." "Do you really?! You never struck me to be the type to!" To be honest, I was surprised she was so shocked, but then it hit me we had never discussed it before. "Yeah, and I'm very open about it," I said - looking her straight in the eye. Then she really surprised me. "Do you...want to do it now?" "I've been thinking about it, I've got some time before class." "No no no, I mean masturbate with me." "When, where?" "My house, it's not that far, we can get back here in time for class." I grinned at her. "Alright, let's go then!"
On the walk there we established rules and boundaries, no touching the other person, all clothes must be off, moaning is allowed but no dirty talk. As all this was agreed I kept imagining her naked body, the one I had fantasised about masturbating the night before. We also completely opened up and discussed everything, how often we did it, our porn habits, why we did it and so on. My cock was getting harder and harder just hearing her talking about this.
When we arrived at her house she opened the door, checked her parents/siblings weren't around and led me upstairs to her room. It was large but the only place to sit on was the bed. We agreed, I sit at one end while she lay on the other with herself exposed to me. With that decided, we set about undressing.
She's really cute - thin, small tits and shaved. She slid off her pants first, then took off her top. I looked at her in her bra and panties - my cock was just itching to get out and be played with. I took off my shirt first and then slowly my pants, the moment she saw the outline of my hardon sticking out of my underpants she giggled uncontrollably and said "well he's eager to come out and play!" With that she undid her bra and let it drop to the floor, letting her small perky tits bounce. She squeezed them and said "so what do you think of them?" I just looked and said "they're awesome." We looked at each other, her in her panties, me in my underpants. I said, let's take them off together, on the count of three." She nodded. "One..two..THREE!" We both hastily dropped them to leave ourselves completely naked. We looked at each other once again, this time completely naked, and giggled. "I think we should get started," she said. We took our positions.
She started by slowly circling her pussy with her finger - licking it and circling, over and over. I started slowly with small stroked to my pulsating cock. It had been yearning for me to touch it for some time - there was plenty of precum that oozed out of it. I watched her as she circled her pussy faster and faster - then she started rubbing. She moaned and looked at me, I groaned and looked back at her. While this continued we continued talking about masturbation, sex and such. Just watching her was making my cock so hard - my strokes became larger and my hand gripped it harder. As she started to rub harder, her breathing became heavier and her moaning more frequent. Soon, she stopped completely. She lubed up her two fingers, looked at me and said "I'm going in." From there, she fingered herself to one orgasm after another. She shoved her fingers inside herself and pumped them in and out of herself so hard and fast. She was in her own world, her eyes were closed, one hand squeezing her boob the other fucking her pussy. After every one, she would stop, lick her fingers and start again. I too started getting faster, I stroked my hard cock until I felt I was almost there. Just when I felt I was there I shouted "oooohhhh yes I'm cumming!!!!" I had an amazing orgasm that rocked through the entirety of my body - my cock shot out layer after layer of warm, sticky cum onto my chest. After she came one final time, we both stopped, looked at each other and laughed. "You were so into that!" I said. "I know," she said, "I must have had twenty orgasms! It was so much better watching someone masturbate that wasn't on a screen!" "Yeah, I agree!"
From there, we did it every week. We haven't and probably will not go further, but now we both cherish our 'masturbation buddy'.