It was nothing

You turn and see your sister smiling and getting dressed. She throws your clothes onto you and orders you to get dressed. On the way home you give her a blowjob and before you go inside she fucks you in the back seat like a prom slut. So begins your new life with your sister, with both a bang and a whimper - from you.

You wake up each morning feeling blessed to be your sister's cumslut. Thanks to her prowess, you are fucked multiple times a day, and it soon becomes routine for both of you. Your parents never come home from their vacation and you soon forget about them. Each room in your home becomes an adventure, and you've been bent over and pushed into every available surface. Not a single part of your body isn't used by your sister in her lust.

Soon, though your sister feels the need for change and adventure, she still fucks you just as much as she used too. After all, you wouldn't survive with less, but she rarely gets into it as much as your first time in that doctor's office. After a time, your sister starts to change small things about you each day: a different voice, smaller or bigger breasts, often how much you want it.

For several weeks, you try and fight her each time, before giving in just like you did early on, but that couldn't sustain her forever. After a series of small changes, your sister decides to go in deep and radically change things.