Since the first time my sister and I made each other cum, I wished we could do it again. But I was too scared to initiate anything like that with her. After all, I had only brought her to orgasm as a remedy to her menstrual cramps and she had sucked me off to thank me for said medicinal orgasm. Sure, it was the hottest, most intense orgasm I had ever experienced and I didn't even have sex with her, but I was sure our behavior that day was to serve one purpose exclusively. Either that or I had convinced myself of this as a way to chicken out of...