This happened last week..Im a 33-yr old guy and I was at a country party at a rented cabin by a lake..the cabin also has a sauna, which is a separate little building just by the lake. The sauna has two rooms, one which is the real sauna which is steaming hot and a front room with a shower, for changing. We were about 15 people having a bbq and getting drunk and bathing and stuff..among them was my best female friend since many years...She's 28 and quite good looking, with short bleached blonde hair, slime body with small tits and beautiful blue-greenish eyes. I've told her I want her but she says she's not interested but she's still quite a tease sometimes, like posing and batting her eyes to me and stuff like that...anyway, we had just had a bath and she had her bikini on which turned me on. So then we changed and had a beer by the bonfire with the rest of our friends..during the time bathing with her I had become quite aroused, and now I felt I had to wank. Fate was on my side, because she went with another girl to sit on the porch of the cabin, and I slowly made myself invisible by pretending to go for a piss but actually went to the sauna. Inside i found her bikini lying on a chair..Through a small window, I could also see her sitting with her friend on the porch, so I thought it was safe to experiment a bit. I started masturbating while sniffing her bikini, especially her pants...her bikini was still quite damp from our last bath..soon I felt myself getting really aroused..so I undressed until I was fully nude. My friends were not far away but I have this thing about masturbating in risky situations...so there I was, totally naked with a rock hard cock. Meanwhile I saw through the window that she got up from the porch and back to the bonfire and talked to some people and they pointed to the sauna house where i was...all happened so fast and as I was wanking I wasn't too focused! THen I felt my orgasm approaching, and just as I realised that she was actually coming to the sauna house I climaxed uncontrollably and in my excitement i squirted my cum into her bikini pants...all of it into the crutch. Then i heard her approaching outside so I kind of freaked out and realised she would notice so i put her bikini down on the chair again and quickly grabbed my own swimming pants and put them on. Just as I had them on, she opened the door and I forgot to realise that just after a nice wank the dick is still hard for a while, and the first thing she saw was the not-so-subtly bulge on my pants and she had huge eyes, then she looked me into my eyes and said
"you're going for a swim again??".
"Sure" I replied.
"Well then I'm going as well, all this BBQ is making me hot".

So I told her i would wait outside for her, and as I got outside I could hear her shuffling about inside and I thought "fuuuck she will see my sperm!" and I felt really really bad for a while. She's my best friend and I realised my cum was still very visible...a thousand thoughts went through my head..i also thought maybe she wouldn't notice too soon because the inside of her pants, which were blue, had a layer of white lining so maybe my cum wasn't that visible..also her pants were still damp from the last swim. But my heart was pounding from the stress of not knowing if she would notice! Anyway, after a minute she emerged, and as she was wearing her bikini I almost fainted... Then as she approached me she adjusted her bikini knickers with her hand, like pulling the crotch as if it was uncomfortable..she kept doing this for a while and then I had to ask "They're quite uncomfortable when they're wet aren't they??" and she giggled and answered "yeeah...they're sort of...i dunno...sort of squishy...". And then I saw before me how my cum was smearing all over her pussy, because i had ejaculated so much into her crotch. My cum was probably still warm when she put her knickers on! I can't believe she didn't notice but I suppose she was quite tipsy and also that her bikini was damp, so if she felt something she probably didn't think so much about it...but here she was, right in front of me, adjusting her pants, and the last thing she did was sort of pressing her hand against her crotch, almost rubbing and this was almost too much for me. I realised only then that I still had a boner and she looked at it and giggled and said "Seems like you need to cool down a bit hihihi"..then we ran to the lake and had a little swim.

This was such a nice memory! I still wonder if she really didn't notice anything. and whenever I visualise how she smeared my cum over her pussy, I always get horny.