The slave is in a floor with a hole for his face, he cannot turn his head away, his face is everytime exposed, ready for some treatement!
First she sits carefully in a schoolgirlpin foreward on his face, gives him the idea of airlessity...
Soon she streches her legs for apply more weight... and less air for him ;-)
Then she turns around and her ass eats his face, nice smell.
Later she moves on his chest and puts her feet on his face, cheesy time.
To the end she steps fullweight on the face until it's crushed.