This happened in college. One night my girlfriend Jen and I were making out in my bedroom. I had one hand inside her blouse and another up her skirt, and it was just getting really good when my roommate Ricky walked in. "Whoa, sorry," he said seeing us. "Don't worry, I'll sleep on the couch." I felt bad because I knew he'd get no sleep outside in the dorm common room, so I pulled a blanket over me and Jen and told him to stay a while. I figured the least we could do is drink a beer with him before kicking him out. I could tell Jen was embarrassed, and I felt her buttoning up her blouse and pulling her skirt down under the blanket.
One beer led to another, and Jen and I had already had some before Ricky got there, so we were getting pretty buzzed. Then Ricky rolled a joint, so soon we were high on beer and grass. I started kissing and fondling Jen. The blanket got pushed off and my hands were inside her blouse and up her skirt again. It got so hot we both forgot about Ricky. When I remembered, I looked over to him and expected to see him asleep (or politely pretending to be asleep), but he wasn't. Instead, he was intently watching as I kissed and fondled my girlfriend.
Surprisingly, being watched by Ricky turned me on, so I didn't stop or tell him to look away. Instead, I unbuttoned Jen's blouse so he had a clear view of her lacy bra. Right around then Jen remembered that Ricky was in the room, and I felt her body tense. Maybe it was the beer and pot talking, but I whispered "Let's give Ricky a show."
Jen's eyes grew wide. "Are you serious?"
I nodded. Ricky heard us whispering, and must have thought we were trying to figure out how to get rid of him, because he said, "I guess I'll hit the sack outside."
Again, maybe it was the beer and pot talking, but I said "Hey buddy, don't leave on our account." I started kissing Jen again, and she didn't stop me when I pulled off her blouse. I reached behind her and unsnapped her bra, then pulled it off her arms and tossed it on the floor, leaving Jen topless before Ricky's eyes.
Jen pressed her palms on her skirt when I tried pushing it up, stopping me momentarily, but I moved her hands and pushed it up around her waist. I quickly pulled off her panties (it joined her bra on the floor), then moved in between her legs. Jen was embarrassed being topless with her skirt around her waist, and me between her spread legs, so she covered her eyes with her arm. But that didn't stop her from moaning when I licked between her folds and flicked my tongue across her clit.
Ricky looked totally turned on. He motioned to a chair next to my bed and raised an inquiring eyebrow. I nodded, and he moved over to the chair. Jen's arm still covered her eyes, but I think she sensed Ricky sitting next to the bed. Now he was within arm's reach of Jen's naked breasts, her flat stomach, her long shapely legs. I knew he thought she was super-hot.
To his credit he controlled himself from reaching out and groping her. But that didn't stop him from unzipping his fly and pulling out his dick. He was big, which bothered me, especially when he gave me a "I know you're impressed" look. He started stroking his meat and if anything he got even bigger. All of a sudden I felt jealous, with him getting hot looking at my girlfriend.
Usually I'd get Jen off with my tongue and then fuck her, but I didn't want to wait. I wanted to show Mr. Big Dick what he'd never be able to do, so I pulled on a condom and positioned my cock between her pussy lips and pushed in. Jen grunted as I did so, and I smiled at Ricky, my message clear: you can look, but she's mine. I cupped her breasts and rubbed her nipples as I fucked her, then kissed her. She finally moved her arm away from her face, but kept her eyes closed. I leaned back and put her long legs over my shoulders and then started to really pound her.
My hard fucking caused her to open her eyes, and she looked at me at first, and then turned her head slightly and looked at Ricky. Well, not at Ricky's face, but his hard cock, which was just inches from her face since he was sitting right next to us. I didn't fault her for what she did next. By that time we were all lost in lust, and it seemed like the natural thing to do. But when Jen's lips formed an O, my head practically exploded.