This slave had spoiled a very expensive gadget and of course he could not afford to pay for it. So the mistress had to find a way to make him pay for it. She chose to force him to endure being ass fucked. The mistress used her strapon to fuck him in the ass and that was the payment he had to make for the gadget he had spoiled. She bought another one after that.
This mistress was horny and she was ready to get hammered by someone who had a big schlong. But it so happened that the guy she had chosen had a small one. She was disappointed in him because he had bragged about how he would rock her world and how big his dick was. Her disappointment led her to humiliate him by making him lick her boots instead of having sex with her.