My sister-in-law sucks it until I it

My sister-in-law took advantage of her stepsister leaving so she could come to my room and ask me for a favor. And since I charged her and she had no money, she told me that she sucked it so well that this would be her way of paying whenever she wanted something. Then I suck it and as if it was delicious I ended up it. She screams so good, that I can't stand to give her more and harder. He said that it was so good that he will want me to always suck it.