If you get confused, read through the terms and phrases section, where we've done our best to cover every picky detail.

Unless directed otherwise, you must now replace every card you have taken off the board with a card from your hand. Replacement cards are always played face up, execpt when you are directed otherwise.

If your opponent is responsible for replacing cards during your turn, because he popped some cards or because of some other card effect, you and your opponent take turns replacing, starting with you.
(게임에서 pop은 카드를 가져가는 행위를 말합니다)
If you're unclear whose reponsibility a certain card is, just ask yourself "who touched it ?". It should be obvius in each case who actually touched the card. The player who picked the card up is responsible for replacing it.
When you are replacing it's usually a good idea to leave no desirable moves for your opponent. On the other hand, if you're going to take the next turn, this is your chance to set up the perfect move.

뭔가 아리까리한게 이상해서요. 고수님들의 도움 부탁드립니다.