Japan is one of the biggest market for stuff like that and no one there would take a look at this if it was like in the novel. The old hate between s.korea and japan, i guess after it took off the people behind the marketing stuff wanted it a bit streamlined, to avoid triggering this hatred more and making the comicalisation more intresting for japanese reader. (even if the original author of the LN seems to hate japan quite a bit deep down, at least somewhat)