The sissy is in training to become a fuck hole, the aim is for the sissy to be able to willingly take really big black cocks that want to fuck her ass, but there is still a long way to go. During this training session the Mistress pushes bigger and bigger plugs into her ass, while the poor Sissy in her predicament just begs for mercy, that she's had enough and her hole is already stretched to the max, but the Mistress doesn't care.  Instead she prefers to sadistically treat the "micro clitty" in the little chastity.  Sissy gets hornier and hornier.