Lyra's behind has become quite the sight, her ass cheeks many times their previous size and having subtly changed shape. Covered in a slowly thickening layer of ginger hairs her rear is starting to resemble the haunches of a cow.
Nestled between her butt cheeks, Lyra's asshole and sex are on full display as her cheeks pull wider. Her pubic hair has spread, now growing in a tuft that blends into the rest of her fur. As you watch her asshole begins to darken and swell, eliciting a squeal from Lyra as she feels the change.
Lyra's voice strains as she says, "It...it's moving...oh my god! Do...don't you dare look!" You hear her but you can't look away as the puckered flesh of her asshole slides upwards, coming to rest directly beneath her tail, her hole winking as it puffs out leaving her with a dark brown donut as she squeals again, louder and deeper this time.
As you watch her transformation Lyra's scent intensifies, thick with the sweet musk of arousal that fills the barn. Looking down, you see juices dribbling from her vagina, the scent of her lust growing stronger with each pulse of your own heart as you feel pressure building in your temples. Seeing her vagina subtly winking you realize with a mix of excitement and disgust that her asshole's transformation has just made her cum.
"Ah! Shit!" you swear as the pressure in your temples suddenly intensifies and two horns begin to emerge from your forehead. The pain only distracts you for a moment though, as Lyra manages to stagger back up onto her hooves you see what part of you has been dreading, but another had been waiting in anticipation for, Lyra's transformation has reached her vagina.