His maleness drools and squirts limply when you slide it out of your muzzle, but quickly stands erected once more when he catches the scent of your heat. You position yourself above it and sink downwards, it feels good to have something inside you. You both take it rough and fast - a different tone to your earlier escapade, constantly shifting postures to accommodate your changing physiques. You're riding on top of him originally, then soon you're the one laying on your back and eventually to doggy style as the bones in your hips and legs crack, rearranging into shapes more fitted for quadruples - complete with the same cloven hooves.
It's only a matter of minutes before you both cry out in unison to your climaxes, antlers budding out prouding from your heads as they loll tiredly against the floor - spent and exhausted.
You cuddle against each other, falling asleep.
=====
If anyone could see you both, you could've been mistaken for regular reindeer saved for your human body shape and your partner's 'anthromorphic' form, that's the sight which greets your partner when he wakes up. Confused at first about how awkward his body seems to feel, he then slowly dawns with terror at the fur and hooves he's sporting. Observing how far gone you are compared to him, then shrieking in soprano when he discovers his... Or rather... HER own changes - Breasts, hips, and her... his shrinking dick getting pulled into a forming genital slit, he tries to stop it and shamefully moaning out loud whenever she hits a sensitive spot.
"Nooo... Ah, aaaaah... No... Please..." He shudders as his dick gives one last pitiful squirt and gets sucked up into her new organ, guts gurgling and shifting aside for a forming womb. She curls at the sudden surge of lust, fingers rubbing against her lips to relief herself. Images of her getting rutted silly by stags flash through her mind, urging her to give in. She shivers at the thought in delight, before she shakes herself out of it and draws her hand away in panic.
"I... We've got to get out of here!" She exclaims, trying to fight through the haze.