The slave has to behave, because if he touches his mistress, he will being beaten by her strong hands and maybe worse, he must suck that ugly, huge strapon that the mistress pulled out of his asshole. But we all know, that he can't behave, he must shout, scream, touch Mistress Christina's legs without permission and moves all the time. So the mistress fucks his ass like hell and hits his head and back when he doesn't behave.