Mistress Zephy was not in the mood to talk to her slave as he had pissed her off. So she used her pee to punish him and since she was in a bad mood, he had to do something to lift her spirits and she chose to make him lick her pussy when he was done drinking her pee. And that is exactly what happened and she was ok with him after that.
These mistresses did not like how their supervisor made their lives hard. He was not fair to them and it was not justified. They had not done anything to him. They taught him a lesson today as they pissed on him. They forced him to drink all of their pee. They trampled him as well and humiliated him like they had never humiliated anyone before and like he had never been humiliate before.