The slave is being educated in the area of rectal expansion, broadening not just his horizons... he is told in no uncertain terms that each day the cocks he must worship and take up his ass will get bigger and bigger. He needs to surrender to their whims or the discomfort will quickly turn to agony. They make him gag on their appendages first, deep-throating each cock in turn, whilst the other Mistress rams his head down on it. They spit in his mouth for a little extra lubrication and just when he feels he can't take any more, they start the anal probing, pounding and stretching!