Okay, so I never bought coins in the Korean version, but I tried looking around. I don't know any Korean, so I had to use a translator.
https://gyazo.com/863bc7af7c79af5be50fcc8a612ddf55
The option that I had bubbled in the screenshot says "Overseas Credit Card." If that is selected, then the only credit card options they accept are JCB (Japanese), Discover, American Express, and Diners Club. So if you don't have any of those, then you cannot purchase them from the Korean version. I personally cannot because I only have Visa. Haha.
I felt very sad... when I saw the MC start crying and the ML just hypnotized him to accept his situation and feel good... It's almost like he got injected with a drug to numb his feelings. The world is interesting, but it could have wholesome.