I grew up in a mid-size city, a middle class family and mostly sheltered from the big city life of Chicago just a few hours away. We didn't have rave parties and orgies, but we knew about them of course. I was the oldest by three years and always very protective of my baby sister. My family and I tried to keep the realities of inner city life away from her the best we could.

The world really opened up for me when I went away to college at Northwestern University. I found the "big city" temptations of drugs, orgies, and parties all in the microcosm of the campus. When my sister Diane turned 18 and graduated High School she joined me at Northwestern. I insisted we share a two-bedroom apartment and naturally my parents agreed. It made sense to save money this way and besides I would be able to watch over my virginal baby sister and keep the wolves at bay.

Boy was I ever mistaken.

The arrangement would cramp my style a bit. I was currently dating the wildest woman I ever met, Lila. She was an art major who rocked my world. She was a little shorter than I at 5'9 and volunteered to be a nude model at the art department. She worked at the local Hooters wearing those orange short shorts and skimpy white tank tops that really accentuated her 38C chest. We had dated for a couple of weeks when we started having sex regularly she was nearly insatiable. She would want us to role-play. I would pretend to be an art student and she would model and I would change her poses resulting in sex. Or she would pretend to be my French professor and seduce me.

We acted out our fantasies and it opened a new world for me. Then one night after sex we cuddled together and she told is she was bi-sexual. She also stated she would love to have a threesome with me and another girl. I was intrigued. Okay... I am a guy... so I was very excited. Since then wherever we went and saw a beautiful girl I'd whisper to her "how about her?" She would play along in a teasing way, but it never really materialized and after a week or so I just dropped it as one of her fantasies.

When Diane moved in, Lila and I had to curb some of our role-playing activities to the confines of our bedroom. I also felt embarrassed about having sex while my sister was awake in the living room or the bedroom next door, so we either waited till she was asleep or was gone. Most of the time on the weekends, I spent the night at Lila's place.

Diane and I got a long. She made fun of how protective I was of her. I would say stupid things like "Lila and I are just sleeping over because it's late and I don't want her to drive back to her place so late". My sister would recognize these apparent attempts to mentioning sex to her and she played along or teased me with "oh just sleeping eh... sure"

Now Diane is beautiful. At 5'5 she was prom queen, head cheerleader in high school and all that stuff. She is majoring in Drama and probably is destined to be one of those beautiful movie actresses. Most people think she looks a lot like Jessica Alba, but with a larger chest. Perhaps that is why I was always so protective, making sure the guys she went out with were "good guys" not slime or perverts. We both new and even Lila told me she assumed that my sister was having sex when she went out on dates, however, I didn't want to hear it or know about. My ignorance in her sex life was my bliss.

Let me defend myself here. I was protective but I wasn't fatherly. Diane had her own social life. She would drive out to parties or her girlfriends and go out on dates. The fact being that the more she was away from the apartment, the more fun Lila and I could have.

All that was the setup... now comes my story and perhaps you can help me with my problem.

Diane went out to a party and it was going to be one of those all nighters. I finished up at the library and raced home because Lila was going to be waiting for me to do some special role-playing she had planned. It was about 10:30 PM and I saw that Diane's car was gone from her assigned parking spot. I saw Lila in the guest parking and raced up to the apartment.

When I opened the door I saw the lights were off except for a couple of candles. There were two empty bottles of wine on the coffee table and some soft music coming from my bedroom. I grinned, wondering what Lila had in store for us tonight. I silently opened my bedroom door and saw in the dim candle light Lila nude on my bed facing down, her ass facing the door. I smiled and started taking off my clothes but then I her moaning and as my eyes adjusted it dawned on me that there were two people in the bed. In fact there was another girl under Lila and they were in a 69 position.

"She did it" I thought. She went and got us another girl. This was what she was planning and she picked the perfect night when my sister was gone.

I quickly undressed and moved to end of the bed. I couldn't really see much of the new girl since she was much smaller frame and her face was buried in Lila's pussy. The girls head was at the foot of the bed and Lila's legs hung over. Not to startle them I gently placed my hands and rubbed Lila's ass and hips. She moaned with approval as I began to lick and nipple at her ass, all the while trying to get a glimpse of the girl underneath without luck.

My cock was so hard watching this action I rubbed it along the crack of her ass while holding her hips. She stopped snacking on the snatch long enough to whisper a horny "yes" as she buckled her ass upward a little to allow me access. My cock found it's way easily into her very wet pussy. The girl underneath her didn't seem to mind, in fact I could feel her tongue running along my cock as it drew in and out of Lila's pussy. As I started pumping her faster the girl underneath licked my balls and when she took them both in her mouth I came in force. My own knees buckled and I climbed onto the bed leaning up against the pillows and backboard in a halfway sitting position.