do they know that you could literally walk on foot from europe to africa, to the middle east, to asia. they're all connected by land without some invisible forcefield stopping anyone from crossing. the umayyad conquest of iberia happened in the middle ages, european missionaries and merchants were in china, there was the crusades. it wasn't all neatly siloed-off homogenous nations that didn't interact. the historical/cultural/political/anthroplogical/whatever standards of the time also included relations between different people. especially if you're telling a story involving war, a classic way for civilizations to mingle.
also no one was summoning big giant magical monsters
it's disappointing to hear this line trotted out again. not a deal breaker since i'm used to it by now, but it's still a pretty passé answer. i doubt characters are going to be suffering from dysentery or lice. are you really being true to medieval europe if everyone isn't shitting blood and itchy all the time. even if it wasn't going to be a balanced cast, it wouldn't be a stretch to have a migrant neighbourhood in a larger city or something you visit during a quest, emissaries and ambassadors from different nations featuring in the story even if you don't explore those places in-game. because you're not actually making a documentary or something, this is a fictional story where you can make up whatever you want and there's already hundreds of medieval fantasies full of white psudo-europeans out there.
anyway 'kupka' is a moogle's name, pretty sure that's one of good king moggle mog's knights. is the twist going to be that he's the dominant for a moogle instead of titan