The Bite

You wait for your step-sister in her room after she snuck out. She quietly closes the door and jumps at the sight of you. She begs you to not tell step-mom and step-dad, "it was the last Halloween party of the year and I had to go". She makes a deal if you do that for her, she will do anything for you. Anything. You notice a bite on her neck? She tells you it's just a hickey, then seduces you. Slipping you inside of her, riding you. Suddenly she lays her head back, and when she looks back at you she has fangs!? She milks you dry, you can't move... It was all a trap!