Seeing my girlfriend in action

My girlfriend was invited to spend a weekend at her cousin's beach house. We accepted the invitation, even though we knew that it would probably be full of his friends and went in my car. When we got there, we were very welcomed, but not so crowded: besides our cousin who owned this place, there were one couple and two unmarried guys whom we didn't know. As soon as we arrived, we headed for the beach. Bruna, my girlfriend, caught everyone's attention with her hard-ass bikini flossing. I didn't care, because Bruna is really beautiful and I was even used to the effect she had on men. After a while we were all quite close together and talking animatedly. Around there we made a barbecue and then I noticed that out of all people present my girlfriend paid more attention to one guy, Marcos. She always wanted to talk with him and stay near him, which started making me squeamish. But the barbecues were lively, so I thought it would be better not to bother myself about them. The next day it was the same, Bruna always paying too much attention to the guy. On our way back around the beach I couldn't resist and asked her what was going on. She got bored, said she could not stand my jealousy etc. Didn't want to spoil our weekend so I apologized. We reconciled with each other and went back to the people who were already preparing another barbecue. But even trying to disguise it, it was impossible not to notice her interest in the guy; that curiously started arousing me quite a bit, and I had a strong erection when imagining her with someone else. But I preferred not to confess it to her and let things happen naturally, and in the evening when we had sex gave me an immense desire to imagine that she was owned by another. The next day (which would be the last before returning home) spent morning paying attention to them, but nothing happened except for one hour where he asked him because they were closer sunbathing on his back. I was a little bit off at the time, and saw from afar (with an incredible hard-on) that guy's hands were gently smoothing her back; he had already almost reached his butt when other people arrived so he stopped, I guess to avoid causing any kind of suspicion. When I had the opportunity to be alone with Marcos, I asked for complete confidentiality and although not very intimate with him commented on my fantasy. He who was a discreet and respectful person remarked that he really perceived my girlfriend's interest in him but it didn't mean she actually wanted something from him. I replied that I could see how she looked at him and was sure if I wasn't there and he sang maybe she would give up even though she already assured me that she never cheated before. He then said that he would like to see her give it to someone else, and this could very well be the one who had attracted so much attention from her. Then he said that if I agreed, she'd eat Bruna with great pleasure. So we deliberated on how to make this fantasy come true in view of what was going to be our last night there. So, at bedtime I complained to Bruna about the heat (which it really was) and suggested that we go into Mark's room. She found this idea strange and reluctantly went in, but as much as I insisted she agreed. When I got there, I had the impression that she became a little uncomfortable. On purpose I spread out on the floor an awkward thin mattress. We lay down and turned off the light, me and her on the mattress with Markus alone in bed. But soon afterwards she started complaining about the hard ground (as I intended); so I suggested she sleep next to him in his bed. She was surprised by my proposal, but Marcos intervened and said that there would be no problem at all, and the bed is spacious and she will feel much more comfortable than on a mattress. She refused, saying it didn't fit, but we insisted it had nothing else. So she gave in and went to his bed (she was wearing a sexy black shirt with lace panties underneath while Marcos was only in her underwear). We exchanged a few words, and then we were silent in the twilight (the room was not completely dark). I kept my eyes half open, pretending to be asleep. After some minutes passed like it had been arranged, Marcos started acting up. I saw his hand slowly approaching her leg which was exposed. She got a jolt when she felt the touch, opened her eyes but didn't say anything. Just moved further away getting closer to the edge of the bed. Marcus in turn drew nearer and smoothed his leg again. She had no choice but to fall off the bed; she held his hand and pushed it. I noticed that he bent her waist toward her, as if placing a stick in his little bundle, and touched it again. She took hold of his hand once more, as though trying to pull him away, but having lost all strength, let his hand smooth out her thighs. Marcos then brought his face close to her neck and began kissing her gently, causing Bruna's face to contract with an expression of pleasure. Needless to say my cock was almost exploding, but I couldn't punch because Bruna would have seen me awake. I saw his hand with the hard stick go over my girlfriend's body (who was on her side, facing me), causing her to twitch in excitement. He patted her breasts, smoothed out her knotty tummy, stroked his little cheek above her panties as he rubbed it against her delicious ass. She no longer held back the moans as if she didn't care that I understood. Unable to pretend sleep any more, I finally kicked the dick outside and slowly masturbated for fear of making fun soon. Marcos made her sit down and took off his sweater, exposing the beautiful breasts that were promptly fondled and licked. Then he leaned back on the bed, threw his hard stick out and pulled her head. She still hesitated a little but ended up falling face-first into the toilet bowl. I never imagined one day seeing my girlfriend with a stiff stick stuck in its mouthpiece; I didn't resist and enjoyed it abundantly. But my cock obviously remained firm, and I continued to masturbate while watching the buffet. Bruna's mouth went up and down at an insane pace as this guy twitched and stroked her hair. I wanted a camera to film it, that was the thrill of this scene. So he made her turn around and take off her panties and make her put the mouthpiece on his face. The scene was tremendously exciting: my girlfriend with a hard roll stuck in her mouth as she rubbed the handkerchief against the guy's face. They moaned loudly but luckily the room where we were was away from everyone else. Bruna did not resist the half-nine for long; she held up her body and cried out aloud while squeezing the mouthpipe into the man's mouth forcefully, then collapsed facedown onto the very hard roller. He then stood up, put her in the roast chicken position and opened her legs wide with his dick pointed at a very wet pussy. Bruna was still recovering from that first orgasm half-softly looking on with an immense face of satisfaction. In no time had she gotten herself fully into her vagina going in and out forcefully. She groaned loudly, writhing and squeezing her waistline with her feet. He accelerated the strokes (as Bruna loves) leading my girlfriend to the second orgasm. Then he laid it overhead and asked her to sit down. My girlfriend, half exhausted, obeyed and hugged the guy's dick with pleasure. Then she leaned over him and slowly began a rolling low moan; he helped her by grabbing at her waist and pounding hard. After some strokes, she joked again almost shouting. He announced that he was going to joke; came out from underneath her and asked for his mouth. Brown-faced Bruna barely had time to put her head in the cockpit, receiving an unstoppable torrent of shit she couldn't help but swallow. The guy held onto her head and screamed and only let go after spitting it all up. So they fell exhausted into bed, and then Bruna discreetly went to the bathroom to wash up. Marcos said that I could stay in bed with Bruna and he would sleep on a mattress. I slept hugging my little whore who was already sound asleep. We woke up late the next day and everyone including Marco had gone away. My girlfriend told me she felt embarrassed and apologized for giving in. I explained how much we loved each other and realized what a delightful fantasy it must have been, which we can repeat in the future, and our relationship has improved considerably since then.