Stretch Mode!

"Alright, I'm kinda curious to see this myself. Pound-O-Matic, initiate Stretch Mode!" Myra says to the machine.

It then replies "You have selected Stretch Mode. The sexual extremity will be inserted into the subject and inflated until maximum size has been reached. Thrusting will occur during the inflation process. After maximum width has been reached and the subject has experienced orgasm, the sexual extremity will be shrunken down to original size and removed. Beginning penetration now!"

You gulp from what the machine explains, knowing that your ass is up for a real challenge today. You can only hope that this doesn't end with a trip to the doctor. The big purple dildo starts moving upwards, ever closer to your asshole. With a hard push, it quickly slides inside your sphincter, making you yelp from its size.

The machine says "Penetration successful, starting thrusting and inflation..."

The machine starts slowly sliding in and out of your ass, making you flinch and struggle the first few times that it does, still breaking you in. After a while of thrusting a weird sound starts coming from the box. Almost like its sucking in air. Then, you notice that the dildo lodged in your ass is getting slightly bigger by the second. Not so much lengthwise, but you definitely feel it stretch out your asshole more than it already is. This makes tears form in your eyes as you start breathing more heavily.

A while passes, and the dildo shows no remorse in thrusting your anus while slowly gaining girth. The dildo has easily become an inch bigger since you started. As the dildo keeps expanding and thrusting, you feel yourself get more and more horny from it. The immense pressure on your prostate has got your dick fully erect and dribbling precum from the tip. You moan every time the expanding shaft pulls out of your stretched out sphincter and forces itself back in. Your moans turn into little cries, as the shaft expands more and more.

After growing another inch, making your ass gape at a staggering 5 inches, your shuddering moans turn into painful yelps every time you get thrust by the dildo. Its rapid expansion is pressing very hard against your prostate, and the repetitive pounding has got you struggling in an odd mix of pleasure and pain. More and more time passes as the shaft keeps expanding in size, gaping your ass wider and wider by the second. You grunt loudly as it keeps expanding and your mind starts going a bit hazy. You try your best to bear the discomfort and find yourself enjoying it more. Inch by inch, the dildo grows bigger, stretching out your rectum and giving you one hefty stomach bulge.

You slightly lose track of time, but around 10 minutes later, the last inch is too much for you to handle. You scream out loud, as the giant purple shaft expands to a mind-boggling 10 inches in diameter, pushing your sphincter beyond what you thought humanly possible. The purple shaft keeps pounding you as fast as your body allows with all of its giant size.

The machine exclaims "Maximum width reached! Waiting for the orgasm of the subject..."

The insane stimulation of your prostate delivered by the monster dildo in your ass sends you over the edge, making you cum. You let out a loud yell, spraying jizz all over the contraption in front of you.

After creaming all over the place, the machine says "Subject orgasm recognized and maximum width reached. Terminating processes..."

The rubber dildo starts shrinking down, like a balloon being blown out. You feel a wave of relief as your insides and sphincter are no longer **** wide open by the fake cock. As the dildo slides out of your ass and goes back to its starting position, you're left with a giant gaping asshole and a heavy breath. You turn your head over to Myra, who seems to be watching intently.

She says "Wow, the max size! I've seen people break way faster, but you withstood all 10 inches, good for you. I wouldn't even be surprised if you could do more than that at this point! But don't worry, my lube will have that hole of yours back to its original size in no time, locked up nice and tight. Now, where were we..."