Dirty Lisa

I'd been dating my girlfriend for about six months and occasionally spent an evening in with her parents and Lisa, her younger sister. Lisa had made it obvious she had a crush on me and my girlfriend often teased me about it. On this particular Saturday evening my gf parents were staying out overnight at a function leaving me, her and Lisa. We'd rented a movie to watch so the three of us settled down to watch it, me and my gf snuggled up on the sofa and Lisa in long t-shirt and panties laid on her front on the floor in front of the tv. My gf commented to Lisa to put some pyjama bottoms on as she was flashing her undies at us, but Lisa just laughed it off. About 15 minutes into the movie my gf had a call from her best friend. She's split from her bf and was in need of some company so my gf asked if I would stay with Lisa until she got back. She said she would return in a couple of hours or so and left.

Lisa and I carried on watching the movie, she still on the floor with her back to me and I laid on the sofa. By now I had a perfect view of Lisa's ass and thought how good it looked in her pale yellow panties. Occasionally Lisa would look round catching me having a sly peek at her ass. She opened her legs slightly and shuffled towards me lifting her shirt clear of her ass. My cock was beginning to stir in my shorts looking at Lisa's slim legs and shapely ass. It was at the same time a sexy scene on the movie had just finished when Lisa jumped up and said she needed to use the bathroom. I paused the movie and sat there awaiting her return. After 5 minutes or so she still hadn't returned so I went upstairs to look for her.

As I approached her bedroom I could hear whispering and thought she may be on the telephone to someone. Her bedroom door was open and to my amazement Lisa was laid on her bed, head back and eyes closed, with one hand up her shirt pulling at her nipples whilst the other hand was inside her panties furiously masturbating herself! She was talking dirty to herself, muttering about a stiff cock and what she'd like to do to it. I couldn't believe I was hearing this from Lisa. It was then I realised she'd mentioned my name a couple of times and she was fantasising about me. I must have made a slight noise at that point as she opened her eyes and looked round at me. She continued masturbating, mouthing these dirty words about me whilst her fingers were rubbing up and down her pussy beneath her panties.

She looked down at the front of my shorts now tenting a sizable erection beneath. Lisa carried on regardless whilst I stood rooted to the spot. She closed her eyes and laid her head back down and continued masturbating. I could see her panties were soaked now as she began to straighten her legs and point her toes as her orgasm neared. She was still talking to herself, about the dirty things I'd be doing to her. Her legs began to quiver and she lifted her ass off the bed as her orgasm overtook her. "Oh yes" she muttered, as I left her to return to the lounge, my cock now leaking pre-cum into my shorts. Several minutes later she returned, sat next to me on the sofa as if nothing had happened, apart from whispering "Thank you" in my ear.