I'm planning to (eventually) make a webtoon, so can I get some help?

at the moment, I'm still studying perspective and anatomy, so I don't want to start yet. (with the art)

My problem is finding dependable resources for the future of my story.

It'll be a isekai (ugh, I know, but I want to make an isekai that won't be terrible cringe haha. Hopefully I actually deliver when I do decide to pull through with this.)

I'm still iffy on this idea, but I may put the girl who gets isekai'd into her inevitable doom, in Korea. Because I am uneducated in being raised in Korea or living in Korea, I'd like to know, realistically, what it's like living there, the traditions, etc..,

And even if I decide to put her previous self in the Americas, she will be of Korean descent and I don't want to write a character that's not realistic to their nationality. Basically I don't want to offend anyone!

(note: even though I'm asking for personal information, I'm going to do my own separate research so I know that I won't, for sure, offend anyone.)

I also need help learning the ways of medieval Europe and the hierarchy works for kingdoms and empires. If anyone has reliable, in depth resources I can use for this, (though, yet again, I'll be doing my own research as well, I'm just curious to see if others have some that I would be useful,) or if you are well versed in such knowledge, I'd be grateful!!

If you'd like to see my art, I'm minauyu on instagram and tumblr! (my insta has more art posted, though)

and if you'd rather dm me instead of replying, then please feel free! I want to do good research for the future of this story so any help is something I'd be thankful for!