One year my sister dressed up as Elvira. She was a dead (LOL) ringer except my sister is about a 40DD. Even though she was my sister the amount of cleavage she was showing was getting my juices working.
I did my usual werewolf make-up which takes about 2 hours and nobody has ever guessed it was me after I get done with all the hair and brown colouring.
We arrived at the party about twenty minutes apart and I tried to keep an eye on her.
As I was sitting on the couch I felt someone plop down next to me. When I turned to see who it was I saw it was my sister. I figured she recognized me, so I started to say something. She smiled and leaned over, giving me a great cleavage view, and asked me if I only had sex doggie style. I smiled and she giggled drunkenly. Then she asked me if I wanted to do HER doggie style. I was at a loss for words. She slipped off the arm of the couch and onto my lap, and I knew she had to feel my hardon. "So, I know you like me," she giggled. Then she stood up, took my hand, and led me upstairs.
She sat me on the bed, and was out of her shroud in about ten seconds. After a few kisses she pushed me back on the bed, and climbed up on me cowgirl style. I felt guilty when she lowered herself onto my hard cock, but not guilty enough to say anything. I ended up cumming three times, twice inside her and once on her boobs. I dozed off and when I woke up she was gone, and when I went looking for her I saw her disappearing into another bedroom with another guy.
I never did tell her it was me. Am I the worst shitheel ever for having sex with my sister?