I'm not sure how this card works exactly. When you refill your hand from an opponent's hand, are you taking all 5 of his cards? Do you pick and choose the ones you want? Do you take a random card one at a time from the opponent until you want to start refilling from your own deck?
The last two come from the fact that it says that both players refill hands, if necessary. If you just get all of his cards, only he would have to refill his hand.
You discard your hand when you play this, so you draw back to 5 immediately out of your opponent's hand. As you play cards, you won't have any new ones to gain from their hand, so you will both have to refill later.