The two were trapped in a cycle of passion. Both remained blissfully unaware of their changes while they fucked. Mark's balls were soon wrapped in a furry sack, and his cock in a smooth brown sheath. He started pumping faster and faster, mesmerized by his wife's blackened twat.
Amy's hands, more like hooves now, started groping at her shrinking breasts. She didn't even register that her breasts were slowly disappearing. When they shrunk into nothingness, Amy instinctively moved her hooves down to her growing udder. Her stomach had bloated to the size of a basketball. Four small bumps formed an almost perfect square, and Amy pulled at them with such urgency.
Her mooes got Mark even hornier. Ironically enough, it also made him grow two long horns from the sides of his head. His nose was black, and seemingly swollen. Mark breathed in, smelling all of the musty scents he and Amy were making. That only contributed to the insatiable hunger he felt.
Mark's hands, now hooves as well, pulled Amy closer. He found he was having trouble pumping as Amy's vagina moved back to make room for her growing udder. Soon, Mark had to turn her over to enter properly. Her gaping cow vagina was right under her engorged asshole. Her tail lashed at Mark's growing snout, and he bellowed.
Amy thrusted her hips back against Mark's furred torso. Her vagina sucked up all of Mark's growing cock. Behind him, a tail of his own began to extend from his tailbone. Mark's nostrils flared as, with one final push, he came.