depending on your former university; yonsei, national, international, etc. If you were an undergrad at yonsei, the process is more likely to be a mere formality. The professors already know you, so the result is pretty much settled.

I did my interview with faculty members. The questions were mostly about my research interests and my working style. I believe most people would get accepted as a graduate student if he/she has a strong interest and motivation in academic research.