"Ew ew ew!" Your girlfriend squirms, standing and turning away from you as she hurriedly removes her cum soaked pants, flicking them away in digust with her foot. Sitting up you open your mouth to apologize but freeze as your eyes fixate on her huge ass, barely contained by tight black panties.
You feel your swollen balls pull tight, aroused by the glorious sight of your girlfriend's big butt you forget for a moment the situation you are in. She seems to be troubled by something as she twists about, her hands grasping at the material of her underwear, they look to be very tight and hazily you try to remember if her ass had always been that big.
Snap! the dull twang of stretched fabric reaching its limit pulls you back to reality once more as your girlfriend's panties suddenly give way, exposing her slowly expanding behind and eliciting a shriek as she finds herself holding the ruined clothing in her trembling hand.
Now completely nude from the waist down she slowly turns to face you again, "I.. I think your cum did something to me..." She trembles, as love juices start to run down her fattening thighs and she takes a hesitant step towards you, biting her lip. Starting from her dripping crotch, blonde hairs begin to sprout from her skin as they spread across her lower body.
You shakily stand on your new hooves, intending to comfort her, but your vision flashes white as you feel an overwhelming stretching sensation in your lower back, accompanied by twin pains at your hips, what is happening to you now?