Of all the three holes Master could and would penetrate, Master had said His absolute favourite was the mouth. A human mouth is designed for survival. Food, water, even sometimes air enters the body via the mouth. It is a means of verbal communication; something that makes human beings the most superior creatures on Earth. For Amber though, her mouth had a far superior purpose. A privilege that would put her among the most fortunate human beings in the world. Her mouth was to become the home of Master's cock. It was a shame that Master had to contain His cock inside His impersonal briefs and layer it with denim or cotton pants/shorts. Amber's mouth was where it belonged, that was where He'd park it. That was where it would stay unless He decided otherwise.
Before Amber could ask, He also went further and explained that that essentially meant everything that came out of His cock would end up in Amber's belly. Amber had only heard of the male semen, and had maybe seen it sprayed on a girl's face in a porno. She didn't know if it was edible. Master explained both urine and semen was ingestible, digestible and safe. She need not worry.
Amber had no idea she'd be made to drink urine. She felt very uneasy. She didn't know if she had discovered her first hard limit. Master suggested there's only one way to find out if her limit is soft or hard, or not even a limit. Preferences and tolerances change with time, she was very much a newbie and that He would be mindless if He subjected her to everything all at once. Of course He'd ease her into drinking His urine straight from His cock. Master said He required that of her if He was to truly make her mouth the home of His cock. Amber said she really really wanted the privilege of calling her mouth the home of her Master's beloved all-powerful cock, and she'd be open to doing anything to earn the right to Master's cock.
Master detailed His plan of getting Amber used to His urine. He said He would initially have Amber kneel beside the toilet in the washroom while He stood in front of it and peed in it. Amber would see His urine come out His cock, and follow the sight and sounds as it splashed in the bowl and splattered into the water in the bowl. It would also make Amber familiar with the smell of His fresh urine.