If the people want to a democracy than it should be so and they should not have to ask permission from other countries and it should be better off as well as the whole region if they were to unify the Korea into one government as opposed to it having to sides.
A united Korea would be great as long as it was democratic. That would require the complete collapse of Communist North Korea, which is one of the most oppressive countries in the world and is very hostile to the west. If you could make North Korea like South Korea, that would be a great asset to freedom-loving western countries.
The question is worded as though there are only two options, Communism or Democracy or at least that's the inference. We (Any other Country who has the ability to make such a choice) Should stay out of their business. The very reason they are where they are today is because other countries keep meddling in No Korea's affairs. Let them decide on their own. They are a sovereign Nation and if you don't agree That's fine just don't interfere with their sovereignty.