Alexa walks a short distance, and the "tarp" of her panties is removed from your vision. What you see quickly dismays you, however. Below you, you see a toilet; the bowl looks enormous from your altered viewpoint.
"Alexa? Wait, don't do this! Anything but this!"
"What? You're my ass now, and this is what asses get used for!" She takes a seat on her porcelain throne; the seat feels cold on your cheeks as they are spread wide, exposing your hole.
"No, Alexa! You can't do this! I'm your boyfriend, not just some body part!" Alexa giggles and ignores you. You feel her clench her intestinal muscles, pushing a mass of something downwards. You feel it at the back of your throat: a solid log is rolling out, soon to slide out of you.
"You might not realize it now, but I'm sharing a very intimate experience with you. This is an expression of my love, as much as it is a lesson. You are the only man who has ever gotten to be the hole I shit out of. In time, my ass, you will understand."
But you don't want to understand. You don't want to be a helpless, dirty hole on your girlfriend's body, but there is nothing you can do to escape it. Alexa's turd slides lower, poking past your "mouth". To your surprise, not only can you taste it, but it tastes strangely delicious!
"Mmm that's right. I made it so your taste is reconfigured. My shit is gourmet to you now. It won't be long before you're begging me to take another trip to the ladies' room to "feed" you!"
Alexa lets out a sexy moan as her log slides the rest of the way out of you. You can feel her involuntarily buck her hips as it hits the water with a splash. Your stretched hole quivers with pleasure. Releasing that poop felt like cumming, a pleasure that enveloped your entire being.
"Ah! Oh yeah! Keep going!" she pants as another piece of crap spurts out of you. You realize that she's getting off on this, and so are you!
"Plop!" goes the last of it as Alexa finishes crapping. She pants as she tries to recover from her poop-induced orgasm.
"That's right, Butt. I also changed my sexual response, so using the bathroom makes us orgasm! We're going to be such a buttslut, aren't we?" She gives you an appreciative squeeze as she stands up and wipes you off. You are equally excited about how good that felt, and horrified. Your girlfriend turned you into a disgusting shithole, and she twisted you into liking it! As she flushes, your mind oscillates between disgust, anger, and arousal...