This was the best part of it as far as Mary was concerned. Transforming itself was a rush, a surge of endorphins overcoming any physical pain of a shape that wasn't meant to change changing, of a species meant to remain static becoming something else. When you coupled that with the physical intensity of intercourse? It was a sensation unlike anything else.
The exchange of bodily fluids, each containing the potion that made them piglike in the first place, continued the transformation along. With each push, with each pelvic thrust, both Mary and Rob became more and more piglike. Hands fully gave way to hooves, faces stretching further out, barely retaining traces of the humanity they once held. Empassioned moans gave way to excited squeals and oinks.
When it was finally through and the two were spent, they were both more pig than human, right on the verge of total transformation. They lay side by side in the grass, basking in the afternoon sun. It felt so very good to be a pig. So very good.
"Was... was good for Mary?" Rob grunted. His mind wasn't nearly as developed as it was before.
"Good, yes. Much good," Mary sighed, her breath heaving. "Best boar always. Ever."
"Happy," he answered. The doubts from before would surely plague his mind again later. But for now, he couldn't process any.