"Yess! Yes yes! That's it! I'm cumming, brother! I'm cumming!!!" April finally gave into her orgasm just as her brother thrust into her for the final time. She closed her eyes and squeezed her legs tightly around him, just as her pussy tightened around his cock. This was one of the most intense orgasms she'd had in a long time. However, at the very peak of the pleasure, intense pain shot through her body. Her moans of pleasure quickly turn into screams of pain. She knew what this must mean, but she didn't want to believe it. She was 16, basically finished with puberty, she couldn't be thresholding! As much as she didn't want to believe it though, there was no denying what was happening to her body. She dug her fingers into the dirt and watched as her feet became encased in a hard material and transformed into a hoof like shape. Her legs cried out in pain as they twisted in an unnatural direction, settling into a shape much like a horse or cow's leg. The pain then moved up to the small of her back, and a tail quickly grew from where it stopped. Her breasts grew at least two cup sizes in moments, and a strange swelling sensation began to fill them. The changes reached her head, and her ears grew longer. Finally, a small pair of horns grew out of the top of her head. The pain slowly faded from her body and she lay on the grass, speechless, as the reality of what just happened slowly set in.