@Akumu666 It's not Korean because the Korean flag is white with a red/blue yin-yang-esque symbol in the center(there is also 4-sets of black lines surrounding the center, but describing it would be a pain). If I were to guess what type of flag it would be the flag of Hong Kong since it looks similar.
EDIT: Completely misread your question. I thought you were talking about flag and not the actual cover. I dumb.
@Akumu666 because the group tled from the Korean version without knowing about the original I assume. the original was published 2018. the Korean tl (on kakao) was in 2019.