You are past the point of no return when the door to your room opens and your girlfriend enters. Her stunned expression is greeted with a wad of cum and she stumbles backward, tripping over the table and falling against the wall. It is the first time you have seen your cum on her face and you rather like it.
'Ewww,' she whines in disgust, but from the way her nipples are tenting her shirt you know that her body thinks otherwise. As she attempts to wipe the glob of cum off herself you feel your balls churn with an even bigger load and you move toward her, fist pumping your mighty shaft with every step.
'Babe?' she asks, her voice a quiet tremble. She looks up at you with her doe-like eyes, appealing to your decency to not do this, and then her face is gone beneath a sea of white.
Far from resisting, her hands rub down her neck and over the swell of her breasts, clawing away at her shirt until it is nothing but loose rags and you can see her sports bra underneath. To your delight, her bra stretches as the flesh contained within grows. Within seconds the fabric is stretched so thin that you can see her areolas and their expanded size causes you to stamp your foot and unleash another salvo of spunk over her body.
A tear forms in her bra and her hands rip it away to receive your thick donkey splooge directly onto her corrupted tits. Her nipples are black as midnight and long enough to milk with a firm hand. You have no doubt that she is now more than eager for the rough tit-play you have never been allowed to indulge in, but for now you soak them in your seed.
Your girlfriend screams and the air fills with her musty perfume. The smell is tainted with an animalistic scent and you know that her cunt is also transforming into something much more pleasing to your twisted mind. You wonder if she is struggling against the beastial thoughts invading her mind as they did yours or if she is embracing the depravity her mutating body craves, though it matters little; once you bury your donkey dick inside her philly cunt she'll prostrate herself before any equine beast that she sees.
You're so lost in your perverted fantasies that you fail to notice that your legs have become completely covered in fur. There is a load crack and you are blinded with pain as your legs reform and your feet harden into hooves. When the pain is gone you notice that your head is almost reaching the ceiling and you feel a tail swish across your rump. The change exults you. You are truly half animal now and it would be equally beastial of you to fuck a human. You laugh and the sound is more akin to a whinnie.