Back in the 70s when much younger, my girlfriend (later my wife) and I were having a week long end of summer gathering with about half a dozen college friends at my mothers summer place. Being past labor day it was cool in the evening but the lake was still quite warm. We built a fire in the fireplace and we all took off our clothing and went down to the float to swim.
It was cold getting out of that nice warm lake into the 55 degree evening. We all went back up to the house and dried off. I settled down on a reclining chair and my girlfriend sat down on my lap farther up my body than by my penis. She wrapped the towel around her body. The others settled in similarly around the blazing fire. As I warmed up things started feeling pretty good. My girlfriend reached down with her arm that was under the towel and started fondling my penis. I tried to act as if nothing at all was happening. I became erect quickly and soon it was feeling even better.
Unbeknown to me my girlfriend was getting warm quickly and was gradually letting the towel slip open in the front. In the back it was still hanging down and I could tell no difference. Because I was behind her and laid back I really couldn't see much of the others, just some side views of them sitting in other chairs. Meanwhile she is rubbing me more and more. Pretty soon the slippery drops become enough for her to slide her hand up and down my hard fully erect penis. By that time everybody else was watching, which I did not find out until later since I couldn't actually see any of their eyes or what they were watching. They kept a conversation going. I wasn't paying much attention to what was being said. It had gradually turned to sexual things each had seen in the dormitories as my girlfriend kept sliding her hand up and down my penis.
The stories made me hornier if anything. They were getting more and more explicit and everybody was having a good time. In my turned on state I was breathing pretty hard by this time and trying to look like nothing was happening as I was getting closer and closer to an orgasm. Pretty soon the ongoing stories were describing some guy getting a handjob. Apparently several of the girls had been there and got to watch because they took turns telling the story. The girls were describing how his penis was throbbing and oozing and throbbing some more.
My girlfriend appeared to be matching the description of what the girls were describing so she twirled her fingers around the head of my penis as the others were describing it. After a bit it was quite clear that she was being inspired by what they were describing and doing the same to me. I thought it a really nice touch on her part that she was matching each thing described. At some point I missed the changeover as the description went from past tense to present tense. The intensity of her stroking was increasing. My penis started that throbbing before cumming.
One of the girls said 'He's about to cum'. Another 'Look at that throbbing and pulsing'. It was amazing I could feel everything she was describing in her story. My girlfriend was matching the story most excellently. I still hadn't caught on that my girlfriend was putting on quite a show for our friends. Then suddenly I started cumming just as one of the girls burst out 'he's cumming' and they all started clapping and cheering. With a sudden 'huh?' from me I sat more upright and saw every eye glued to my pulsing penis with the cum rolling down it. It seemed to go on forever. I couldn't stop it so just went with it all the way at that point. I had never been jacked off in front of a group before. Then it was my girlfriends turn as everybody cheered. Then things really got going.