IF STEP-SISTER GETS MAD AT HER STEP-BROTHER FOR BEING BAD, SHE KNOCKS HIM OUT AND PUTS HIS DICK IN A BOX.
It makes his balls get swollen and his dick hard, just like She likes to keep him. But if he starts to cum she makes it all stay inside. Blue balls and cock slapping are his punishment. And hearing him scream, while she his balls and shoves her nails in his trapped dick, turns her on. Until he explodes a monster load on her tits and she ruins it for him.