You struggle in his iron grip as fur begins to sprout around your crotch, creeping along your skin with every thrust. Your cock shrinks slowly as the pointed tip of his member pushes it back, pushes it into you even as you try to break free. A low whine slips past your lips as you realize you can't get away, your body starting to feel pleasure in spite of itself.
Your face is already pushing into a muzzle as fur spreads further across your body, his grin widening as he humps, your cock nearly forced out of his sheath. Running his long, flat tongue across his vulpine lips, he says, "Now, you'll be mine..."
Lifting your head to look down at your crotch, you see it happen. the small nub of what's left of your manhood pops free, and his red tip emerges, precum dripping as it bumps against you. Panting, he continues to force himself onto you, your former shaft becoming a small nub as your balls pull into your body, your sack following as it reshapes into a pair of feminine lips. A wet tunnel opens up behind them, made especially for the red meat eagerly pushing its way in.
You've lost, and he's won. You're quickly on your way to becoming a vixen, and there's nothing you can do about it. You squirm, trying to get away, but it's useless as your arms become more slender, fur spreading faster as he's able to push deeper inside of you. White fur covers your stomach and chest in a soft pelt as red fur sprouts from your sides and back. Your legs become shapely even as they alter proportions, feet lengthening as your legs shorten, becoming digitigrade as your toes grow small blunt claws. Your feet have become paws, black fur covering them and going up to your higher ankle.
"I'm out of my sheath now, completely. And soon, I'll be completely in you. How does it feel? Do you like it? I know you do..."