Goddess Kiffa had an issue with her slave because he had chosen to give her the silent treatment. She did not like it and so she punished him for it. The mistress cruelly made him realize that the silent treatment was not the best way for him to solve his issues. That is why the mistress foot gagged him with her bare feet and ensured that he felt a lot of pain.
When this mistress found out that she had gotten low grades for a subject that she loved and was good at, she knew there was something fishy. So she went to sort it out with the professor and he wanted to sleep with her first before sorting out her issue. She was insulted by that and she punished him by foot gagging her and crushing his mouth as well.