VPN 사용에 관하여

Is there anything wrong with using vpn? For example withdrawal problem

Yes, in some casinos VPN is strictly forbidden, but other casinos accept it. It's always better to ask the customer support before you make your first deposit and if they say it's OK, save the conversation. This way, you can prove that you've been allowed to do that by the casino in case they say you did something wrong in the future.