What do you think about the background in Korea?
Absolutely nothing, because with just a country name it's not a background but a location. What mean that it tell absolutely nothing.
Is it a futuristic reunified Korea ? A past historical Korea, and then which period of its history ? Or perhaps is it a past fantasy Korea, but then what kind of fantasy ? I exclude modern Korea, because I assume that you would have also told if it's South or North one.
And anyway, what will be the importance, for the story, that it happen in Korea ?
Most games are set in an undefined occidental country. Few little details can tell that it's more surely this or that country, yet you've to know the said country to see it. There's also the characters' names, what happen often in Japaneses games, but still it's not infrequent to stay inside your community while living in another country.
So, will it be this kind of setting, a Korea that most players will just identify as being "some highly developed Asian country but I don't know which one", or will the fact that it's precisely Korea have a major impact on the story ?
But well, to be honest, this is more questions for you only. It's important to know all this if you want your story to be coherent, but it have absolutely no effects on 99,99% of the players. Few can possibly decide to play the game just because it happen in Korea, but almost none will decide to not play it because of this.