I don't know what came over me. I had never been one to want to prank people let alone my own girlfriend, but the opportunity presented itself and for some inexplicable reason I acted on it.
We were at a party at a friend's house, and she was talking to a small group of people with her back to me. Her t-shirt was short so you could see a small patch of skin between the bottom of the shirt and the waistband of the gym shorts she had on. On one side I noticed just a small touch of white fabric contrasting the black shorts and her smooth skin and realized it must be her underwear.
As a guy, and her guy in particular, I wondered what the rest of those undies looked like. Normally I would let this notion go but suddenly I was filled with a compulsion to see more. Before I could think about it more I went over and quickly yanked her shorts down. She let out a yelp of surprise as everyone around her got a good look at the white thong she had on. I got a nice look at her ass in that thong for my trouble.
We all began to laugh (including her) after the shock factor had worn off and she quickly pulled up her shorts. As some made jokes to her and me, she looked at me and grinned and said, "I'll remember this." as the situation died down and everyone went back to where they were. Since she was laughing about it I didn't take it seriously.
***
6 Months Later
We were getting ready for another party, and I was watching her get dressed. I was a bit aroused seeing her half-dressed and decided to try my luck hoping maybe for a quickie or a blowjob. I wrapped my arms around her from behind and started kissing her neck while pressing my hardon up against her back.
She turned and gently pushed me away saying, "We don't have time for that baby we're going to be late."
I tried to push my luck saying, "Come on baby just a little relief. Watching you get dressed has gotten me worked up."
She giggled and said, "You really are a horny boy." Then she gave me a sweet grin and added, "Hmm I just got an idea. A kind of kinky idea."
Hoping my luck was changing I quickly asked, "What kind of idea?"
"I promise I'll give you a nice long blowjob and help relive all the pressure I know you've built up if you wear a pair of my undies tonight. I bet that'll help keep you ready and waiting."
"Wear your undies? I'm not sure about that. Would they even fit?" I asked clearly skeptical of what she was proposing.
"I've got the perfect pair. They'll fit you perfectly and look really sexy. Ohhh just thinking about you wearing them is making me hot." She said.
I was still not sure, but I've always been willing to do anything for her if it helped me get some pussy, so I agreed.
"Oh, I'm so excited. Drop your shorts and boxers and I'll get the thong for you." she said with glee.
"Wait a minute you didn't say it was a thong." I interjected.
"it's the only thing I've got that will hold you in. Besides it'll make your ass look great. Don't tell me you're not willing to play anymore." she said adding her pouty look she knew I couldn't resist.