I’m gonna hold off voting, but don’t think translating every single real world culture into a SARP wiki article is very useful or necessary. Doing so limits future players into using one creator’s fictional interpretation of something that is much wider than could be put onto the site’s wiki. Some of the best cultural RP in Yamatai comes from players simply knowing cool Norse or Japanese cultural elements to finesse into their writing, and I’ve seen some attempts at codifying real life cultural elements (like Shintoism) actually make it harder to include cool culture because suddenly you have to do it this way on SARP.
That said, I think a good start to including “Korean stuff” would be to include what’s already been put into canon, such as that Miyamae once had a Neko production facility that made Korean-named Neko. Further, it might be useful to simply say that the Korean language/Hangul writing are a dialect of Yamataigo (since that’s basically where it stands right now) and give them some kind of special setting-specific names. Look into where Wes’s Korean-themed characters are from, too, to see if there’s any place that this dialect can be localized to.