It depends on who does it, Solo Leveling was animated by a Japanese studio so the original voices are Japanese
I think it's based on the animation studio that works for the project, if it's from Korean's studio then 100% the VA will be in Korean, as well as if they're from JP's
Oh. So the cultural phrase references might also change right? Like oneesan instead of Hyung and -kun instead of idk? -nim? Does it take place in korea or japan then? Like the setting.
The setting is the one of the manga, about the adaptation of the phrase references, it depends on what the animation studio decides I guess. In Solo Leveling I think they used niichan and such, but maybe in an anime where it's important to the story they might keep it in the original language. Although, the adaptation would tend to prefer the understanding of the audience over the faithful reproduction of the story
I have a dumb question; so when manhwas like Solo Levelling gets animated, are the orginal voices in Japanese or korean?