My friends sister and her dog

Let me start out by telling you a little about myself. I’m a 23 year old guy. I hit the gym regularly so I’m in good shape, 6’2” and 200lbs. I also have the highest sex drive of anyone you’ll ever meet, I’m constantly horny!
So I was staying at a friends house, we’d been friends for a while but I’d never met his family before. The first time I layed eyes on his sister my heart stopped and I had to control myself, you know what I mean. She was short about 5’2” but she had this stunning little body for her age,16. First I noticed her toned, tanned legs in these tiny, tight little pink shorts, you could clearly make out her butt cheeks underneath. And what a butt it was not big beings she was a small girl but perfectly shaped. To go with all that she had a gorgeous face, she was one lucky girl.
I was staying there for 3 days but on the second day my friend had to go to work for a few hours. So I hung around the house and was getting bored so decided to go check out the gym they had in their basement. The gym was in the furthest away part of the basement in its own little section. As I walked towards it I stopped in my tracks and listened. I could just hear these tiny little whimpers. I crept closer to the gym wondering what was going on. The gym entrance was only covered by a curtain which was closed. I lent up against the wall next to the entrance and listened. The whimpering was mixed with some panting and quiet tiny little moans.
I sat down on the floor and peeled just the very edge of the curtain back and what I saw amazed me. My friends little sister was down on her knees, her face was buried into a pillow on the floor leaving her ass sticking up in the air. Normally that would have been enough for me seeing that perfect thing in the air but it gets better. Her shorts were around her knees and her undies most the way down her thighs. But the biggest shock was her dog (a lab) was there, right behind her, licking between her legs! Her dog was licking her little pussy! My heart was pounding, my mind just kept repeating omg, omg, omg! And my cock was so hard I thought it would explode. That was the hottest site I’d ever seen. The dog was licking and licking and she was moaning into her pillow trying to keep as quiet as she could. Her cute little feet were up in the air her toes curled and pleasure. I couldn’t resist any longer and pulled my cock out and started rubbing it while I was watching this all the while wishing I had a camera.
All of a sudden the dog jumped up onto her back. ‘No way’ I thought to myself. It shuffled up behind her humping the air. She was moving her butt around. Then I heard a big gasp and I knew he was in her, fucking her. I could hear slapping and slurping noises and a really loud wet sound. Now she was really moaning and panting like a dog herself into her pillow. I crept into the room knowing she couldn’t see me as she was facing away with her face in a pillow. I needed a better look. I got just a little bit closer and looked under them between the dogs legs. I could see wetness, I didn’t know who’s probably both theirs dripping out between her legs. This dog was really pounding her, I’m surprised he didn’t move her across the floor. A huge ball was hitting against her pussy as if the dog was trying to get it in but she was just too small for it. After a few more minutes the dog stopped thrusting and just stood there. She was still going crazy under him, shaking and jerking, her hands gripping at the pillow. I could hear her mumbling the word cum and hot or something like that over and over. When the dog climbed off her back and this huge thing slipped out of her, I never knew dogs were so big!I could see straight into her little whole it was so stretched. Then this flood of cum flowed out of her. Running down her thighs soaking into her shorts around her knees and dripping onto the floor. Before she moved I took my chance and jumped up behind her grabbed my raging hard cock and sank it into her. She pushed her butt back against me and I heard her say again? She thought it was her dog. I grabbed her hips and pulled her back against me and pumped into her. Her head snapped around after a few seconds and had a terrified look on her face.
‘What are you doing’ she whispered.
‘I saw everything and now its my turn or everyone will know what you did’
she looked like she was gonna pass out but already she was starting to moan as I pumped.
With that she put her face back down into her pillow. I started pounding her for all I was worth. I could feel all the cum both hers and the dogs making everything so wet and I was just slipping in and out of her easily and I’m not small. I was close before we even started so it didn’t take me long and I was shooting my cum into her. I knew she could feel it, she jerked underneath me and gasped again. I slipped out of her and fell onto the floor exhausted. She jumped up yanked her soaking messy cum filled shorts back up and ran out. I watched her leave, her lower half was literally covered in cum, it was an incredibly hot site.
She avoided me the rest of the time I was there and I haven’t been back since so who knows maybe there’ll be another time.