Hi, my name is Michael and this is a story of how my life changed on my sister's 16th birthday. Let me give you a little info, so you will understand where I've been and where I'm going.
I'm 18 years old, about 3 months past my last birthday. I'm 5' 10", I have short, dark brown hair, blue eyes and an athletic body. I play numerous sports in school and workout to stay fit. My sister's name is Sara, she has just turned 16. She is 5' 6" tall, curvy in all the right places, with golden brown hair, blue/green eyes and 34C breasts. She is a cheerleader and is on the track team, so she is also very athletic.

My story started basically three days earlier just as my sister's 16th birthday party was ending, which was when I came in from being out with my friends. I came in to the house, through the kitchen door and I noticed that everybody was in the process of cleaning up after my sister's party, so I offered to help. My mother gladly accepted my offer and said she was going up to shower and get ready for bed, as she ha an early start to her day tomorrow. So, that left my sister and I to finish with the clean up.

We got busy picking up and putting things back to normal around the kitchen and living room areas. It was during this that I noticed my sister was looking really sexy. She was wearing a short plaid skirt, with a low cut white button up shirt and what appeared to be a white demi bra. I knew I shouldn't be seeing her in this way, but I couldn't help myself. It was the first time I'd ever seen her in this way. I felt a little ashamed, but very turned-on at the same time. I tried to focus my mind on what we were supposed to be doing, but I kept letting my eyes wonder over her sexy body, as she went about picking up and cleaning up the party mess.

It was then that I saw her bend over, just a little more than normal, to pick up some confetti paper and as she bent over, I noticed her panties. She was wearing the sexiest, skimpiest pair of white thong panties I'd ever seen. They must have been really small, as I could see most of her ass cheeks as she bent over, but only a very small amount of her panties were visible. I got extremely hard almost instantly upon seeing such a sight.

I tried to get my mind off what I'd just seen by getting her attention, which caused her to stand up and turn in my direction. She asked me what I wanted, I was quick with an answer, as I said I'd get that with the vacuum. She smiled and went about picking up other things and putting up the dishes they had already washed prior to my coming home.

I was glad I'd avoided trouble, at least for the moment. We went about cleaning, picking up and in no time we were done. Sara said she was going to take a shower and then come back down and watch some TV, as she wasn't quite ready for bed yet. I said that I'd take my shower a little later, as I had a few things to do yet.

It was about 10:30pm, I had all but forgotten what I'd seen earlier, when I heard a faint noise coming from the living room. I was sure it wasn't the TV, so I got curious and went to see what I was hearing.

I quietly walked towards the noise, as I got closer to the living room I could see the TV was on, but I couldn't really see the screen, but I did see my sister was laying on the sofa. I couldn't hear the TV, so I quietly walked up to the doorway to the living room. It was then I heard the noise again, it was unmistakably the sounds of pleasure. It was then that I also noticed Sara was watching a cable version porn, and was touching herself. She was wearing her usual long nightshirt, and she was still wearing those thong panties. I was instantly hard again. I knew I should leave, but I wanted to see more, so I crept up a little closer as I needed to be able to see her better. I could see her hands were busy, one in her panties, while the other was rubbing her breast.

I was frozen to the floor, I couldn't move, all I could do was watch my sister playing with her pussy. I was growing hornier by the minute and I was feeling the need to jerk-off. I needed to cum and I wasn't going to waste this opportunity. I undid my shorts and pulled my already hard 7 inch cock out of my shorts. I started stroking it, while I continued to watch Sara finger her pussy and rub her nipples. I could hear her moaning and I thought I could hear the unmistakable sounds of her wet pussy. All this had me ready to climb the walls, I was getting very close to cumming. It was at that time, I heard something that sent me over the top. I came harder than I've ever come before and it was only after I'd calmed back down, that I realized I had made way too much noise.

Sara had heard me cumming and had stopped what she was doing. I came to my senses only to realize it was now me that was being watched. I looked at Sara as she was looking at me and all I could see or hear was Sara fingering her pussy and calling out my name as she was cumming...