Luke bent over to pick up another shirt, and the Great Dane jumped on him again! The impact nearly knocked Luke on his face, but he dropped to hands and knees instead. "You can't still be horny! You did me twice!"
As if in answer, the big dog squatted and started humping against Luke again. Though he knew better, the boy found himself raising up, and the dog found his cunt and drove in again. Luke gasped and shuddered as he was mounted yet again, each thrust feeling like it was rippling through his body. Heat built up and radiated up and out from his rump, and desire and need increased.
The longer the Great Dane mounted him, the more Luke wanted it to continue. Please washed over him, combined with a growing instinct, a primal need to mate. His body was changing faster now, and as he stared with a mix of amazement and horror, his hands swelled and fingers shortened until they had become large paws at the end of canine forelegs. He could feel his face pushing out, his head changing, his whole body altering.
The Great Dane mounting him shuddered in release, but kept going accelerating the final stages of the change. Luke was now a Great Dane bitch, and she could feel her mind starting to alter, her thoughts getting simpler as the transformation started to affect her very soul!