This night wasn't planned. At that time, my girl and I had a traditional, guess you could say "boring" sex life. Over the 5 years I'd been with her, she had consistently maintained that "size didn't matter to her at all". Myself, my girl, and our friend Phil attended a charity event together. There was music, dancing, and alcohol flowing freely. A very festive atmosphere. From the bar I noticed the two of them dancing together to a hip-hop song. Typical positions, the guy basically standing there with his arms in the air behind her,, while the girl grinds and backs her arse up on him. I thought nothing of it I know she loves me. While I was watching them, she almost stopped suddenly, and turned her head around fast to look at him. Her face was red, she was smiling shyly. She said something to him. His face became red as well and he slowly walked off the floor to grab a seat. She came back to the bar by our group of friends and I thought nothing of it. In the bathroom an hour later and it dawned on me, along with a feeling of dread, that the truth was evident. He got hard from her grinding on him and she felt it. I had forgotten that he was known amongst childhood friends for having a thick cock. Judging by her surprised body language, it was clear that this fact was new to her. I felt turned on, and excited thinking about her shapely bubble butt In leggings getting him hard. When the party was winding down, they played one more song, a slow song, and dozens of drunk folks grabbed a partner and headed to the floor. My girl grabbed me to dance the last song. Whatever force was controlling my thoughts and actions that night spoke up and said "My back is sore honey, why don't you ask Phil if he'll dance with you"? I was then at the bar now watching them slow dance. She rested her head on his shoulder, and tightened up the embrace her arms had around his neck and shoulders, pulling him closer to her body. I noticed that his hands that were holding her waist and hips began slowly moving to the small of her back, and then wandered to the top half of that firm arse. While they swayed to the music, I noticed her sticking her left knee out a bit. She was pushing it into his inner thigh gently, in a slow circular motion while she was staring into his eyes, her mouth slightly open, and I could see her back heaving up and down cause she was breathing so heavy. Few minutes before the song ended, I went to get the car to beat the rush. I grabbed her sweater off the barstool and brought it to her. I draped it over her shoulders. It fell straight to the ground because she wasn't paying attention to anything but getting the best angle, and pressure to stroke his cock with her knee without it being obvious. I picked up the sweater and started tying the arms around her waist under her belly button. With my arms around her body I could feel heat radiating off her. Her bare skin was literally hot to the touch, and her breathing was off the charts, laboured. Using the sweater as cover, I stuck my hand down the front of her leggings, over the lace panties to feel the crotch soaked through. I could feel through the underwear her pussy lips were swollen, and hot. This gave me an erection, so hard it was uncomfortable. While driving home I took her hand and placed it on my dick and she started jerking, at this point there were no more secrets, I took her left arm and guided it into the back, and in Phil's lap. As she jerked and squeezed his cock her breathing ran in sync with her strokes, she was literally in heat, I've never seen anything like this. We get home. She went to the bedroom and stripped off the leggings, and her soaked panties. She pointed at, and motioned for Phil to stand in front of her. She dropped to her knees, ripped his pants and boxer briefs down to his ankles. She grabbed his stiff cock with both hands, and let out a long , slow, almost whimpering sigh. She was looking at it from different angles as she squeezed and stroked it. She began licking under the head, and up and down the length to get it wet. She was whispering to herself "I’ve got to get it nice and wet first, nice and wet". She opened wide and got the entire swollen, shiny, maroon head in her mouth and let out a proud, satisfied breath as she sucked and licked all around the rim. Eventually she got aggressive and deep throated most of it. She had a hard and fast up and down motion with the loud gagging sound when she bottomed out. She repositioned from kneeling, to sitting with her arse flat on the floor. Her back was against the edge of the bed, her feet flat on floor and knees bent. She motioned Phil to bring his cock to her, and asked me to bring over her favourite dildo. She spread her knees apart and started fucking herself fast and hard, filling the room with "slushy" noises as she got his cock back in her mouth like it was food and she was starving. After a few minutes she seemed to be let down with her dildo, like it wasn't getting the job done. She jumped to her feet, falls backwards on the bed, spreads her legs and grunted, "I need this in me now" pulling Phil, and his cock towards her hole. As she was lining the head up to her hole, she said to Phil, "Go as hard and as fast as you can, ok"?? He said, "you want this cock nice and deep right"? She whined, "yes please, fuck me with this fat hard cock now"! Phil thrusted forward, the cock head slipped into her pussy now. After a few strokes when he pulled back, he slipped out of her pussy and his wet cock slid up in between her wet pussy lips and over her clit. It immediately caused an unexpected eruption of squirt shooting out of her pussy like a geyser. She lined his cock up again, this time working the entire head inside her first, while whimpering "Your fucking head is pulsating inside me, holy shit, oh fuck, oh fuck, I'm fucking cumming holy shit”! With her body still shaking, Phil kept thrusting inside her, so deep his balls rubbed against her arse. She let out a deep, echoing moan, and as he pumped, she had another powerful, 20 second orgasm. She fucked him doggie, reverse cow girl, and rode him while having an orgasm every few minutes. There were fountains of squirt blasting out around his cock with hardly any warning. After he came in her, she demanded it. She fell into a coma-like deep sleep. Yes, I just wrote a novel because I never want to forget that night and I really enjoy reliving it. Before this night, if someone told me that I was going to watch another man fuck my girlfriend, I would have called them a sick depraved pervert of a person. It happened, It wasn't planned in advance, so the events of that night flowed naturally and seemed very normal. As of right now, the positives of what I watched that night, as far as the sexual excitement it provided me, outweigh the negatives. Phil went and slept in the lounge. I crawled into bed with her and dozed as she slept. About 2 hours later she woke and cuddled into me. She apologised for letting Phil fuck her. She said she couldn’t help it, she just wanted it. I told her how I liked it and how amazing she was. She wanted me to fuck her. I would love to say that I was as good as Phil had done but would be lying. I made her cum and it still was a good fuck by our standard. Phil left early next morning, we never heard him leave. We haven’t seen much of him. My girlfriend says she is happy that it happened but doesn’t want it to be a regular thing as it would affect our relationship. What remains With my own ears I heard the noises that came out of her while riding his big dick. I've never heard those sounds while fucking her. I watched her orgasm, and squirt 10 or 11 times in a pretty short time span. I am content when she orgasms through penetration with me.