As Jeff wiped his mouth from Sarah's milk, his cell phone rang. It was his mother.
'Hey, Jeff,' she said. 'Your father and I are thinking about extending our trip for a few more days, would that be alright with you and Natalie?'
'Fine with me,' Jeff responded, 'Natalie's asleep, but I guess she'll be fine.' His mother hung up, leaving Jeff and Sarah free to experiment, as long as they didn't wake Natalie.
Jeff looked at his girlfriend's leaking tits. Her milk was delicious; he would love to be able to drink it all the time, he thought. Jeff began to think about his girlfriend being milked like a cow, providing him with sweet milk all day long. The idea of Sarah mooing with pleasure turned him on, and his dick began to harden once more.
'How about we turn this up to 11,' Jeff asked. Sarah, now obsessed with her milky breasts, did not object to her boyfriend using the Chronivac on her.
'I'm gonna make you a human cow,' He said, Sarah squealing excitedly.
First, Jeff gave her a pair of cute horns, which protruded from her forehead. He made her ears similar to a cow's, drooping down to the sides. He gave Sarah a habit of mooing when she talked, and gave her a bovine tail extending above her ass. Speaking of her ass, it would become much larger, as Jeff added a lot of fat to her body. Her boobs expanded even more than before, leaving her with a cleavage that you could get lost in for hours. Sarah's pussy was shifted more to the back of her legs, settling underneath her asshole in a more bovine shape. Her mouth and nose pushed out slightly, giving her a cow's muzzle, which was perfect for eating grass.
Sarah's now muscular legs reconfigured themselves into an ungulate form; her feet becoming black hooves, and making her taller than before. He also made it uncomfortable for her to wear clothes, forcing her to leave her bovine body exposed at all times. To top it all off, Jeff gave her a fat pink udder between her legs, which would need to be milked often. Sarah mooed uncontrollably as her body shifted, her new tail waving wildly behind her. Jeff groped her breast, milk shooting out onto the floor. He started suckling her nipple again, as Sarah continued to change.
As Sarah's body finished its transformation, she gave a loud moo, making them both laugh. Her panties made her crotch irritated, and she ripped them off with her newly enhanced strength. She was taller than him now, and he was now the perfect height to feed from her tits.
Sarah sat down on the floor, spreading her legs as her milk formed a puddle underneath her.
'Come here big boy,' Sarah said, grabbing one of her udder's teats, milk shooting out of it. Her new deeper and more sultry voice made Jeff's cock rock hard as he crawled on his hands and knees towards her udder.
Jeff put all four of her of her teats into his mouth, sucking hungrily as her milk filled his mouth again. Sarah stroked his hair as he sucked her teats, mooing loudly, her tail swooshing wildly above her ass.
Jeff felt like he died and went to milk heaven. He was so glad his girlfriend would let him transform her to satisfy his fetish; he was lucky to have her. Jeff continued to fill his belly with milk as he thought about how to use the Chronivac next.