Looking into you and your partner's "playtime" drawer, you see, among many other items, a buttplug. A very disturbing thought comes to your mind immediately after. What would happen if you put it in your mouth? You tried to keep the thought out of your head, but it just wouldn't leave. After much thinking, you pull the buttplug out of the drawer, before staring at your reflection on its metallic surface. Now you want to put it in your mouth, but it feels wrong. It's like skydiving; your brain says yes, while your body says no. Even though you know for a fact that it is clean, you decide to wash it anyways.
After about 20 minutes of internal struggle, you finally open your mouth and slide the piece of metal in. It feels like it fits more snugly than it should. The strange feeling makes you panic and quickly pull it out, which gives you a small wave of pleasure. You walk over to the mirror to look at your face. It's done. Your mouth is now an anus, all puckered up in an "o". You try to say "Oh god," but you don't have a mouth to say it now, which only makes you want to say it more.
You begin to panic more, wondering if you have anything in the dresser that could change your mouth back. Eventually, you come across a red ball gag. You never liked bdsm, but your partner did. She only made you wear it once, but it was the last time it was worn by anyone, so the dresser should consider it yours, meaning you won't get your partner's mouth. Before putting it on, however, you hesitate. You still want to be able to eat, breathe, and talk through a mouth, but you also want to explore having an asshole on your face. That gives you two options: replace your navel or replace your original anus. You considered replacing your other asshole, but there isn't a way to wear the gag around your ass while also keeping it flush with your hole. Besides, you wanted to see if the change was instant or not, and you can see your navel easier than your anus.
Putting on the red ball gag was harder than you first thought. Adjusting the tightness of the strap was difficult as hell, and you almost broke your fingernail doing it. After much struggle, you finally got it loose enough too fit around your stomach. Looking down to put your legs through the gag strap, you are reminded at the fact that you still have hands for feet, which you had forgotten about already. Eventually, you get the strap where you want it to be, so you get in front of a mirror to watch your belly button become a mouth. Putting the bright red ball over your navel, the change happens within only a second or two. You only notice two changes: first, the hole gets larger to accommodate for the ball; and second, the top and bottom of the hole swell up, turning into your lips. As the quick transformation ends, you let out a quiet moan from your new mouth. You immediately go to take the gag off before the strap squeezes you any tighter.
Looking back up at your face, you now feel somewhat turned on by your donut anus sitting on your face. Seeing your penis become erect gives you an idea. You bring your dick up against your belly, which puts your dick within your tongue's reach. Instinctively, you open your mouth and lick your cock, nearly bringing you to your knees. As you lick your member some more, your eyes wander back to the dresser, giving you another idea. You remember putting your crotch cup in your underwear drawer. You reach in and grab it, before wrapping it around your right hand without a second thought.
Taking it off, your hand has been replaced by a pair of balls and a cock, the latter of which is already getting erect, soon to be ready for action. Reaching up to your face with your face with your cock hand and down to your ass with your left, you make rings around both your anuses with your new dick and your fingers, before going all in with both. Your knees quickly buckle from all the pleasure you're receiving. Licking your cock, buttfucking yourself, and fingering your other ass is proving to be too much for you to handle. You release both of your loads: one into the air, and the other into the ass on your face, making you arch your back and moan harder than you ever have before. Then, without any delay, post-nut depression hits. Hard. You clean up and slump down on your bed. You look like a freak. What would your partner think?
Suddenly, you hear the front door open. Speak of the devil, she's here.