It's mostly in Japanese, not Korean.
The reason it is like this is because we are based on the Japanese Mabinogi server, and do not have the original English locale.
As such, we must translate every line ourselves. This is a large undertaking as the game contains an extremely large amount of text.
Unfortunately, there is not really a way to fix this without waiting for us to translate more text over time.
There is no ETA for translation completion, however quests are 90% translated and 98% of items are translated.
NPCs are only about 3% translated - this is where you would see the biggest trouble.
The NPCs aren't a big deal, but I wish the NPC buttons were translated, especially for part-time jobs. I've accidentally cancelled 3 part time jobs instead of completing them just because of that...