1) labour in the fields
2) don't have skin whitening creams
Quick question for you: Have you actually conducted any research on this imbecilic theory of yours (that North Koreans are quite tan when compared to South Koreans?), or are you basing that idiotic claim on the fact that you've seen a few photos of North Koreans that were more than likely taken randomly in spur of the moment instances where the people being photographed were simply going about their daily lives versus the wide majority of photos of South Koreans who regularly undergo a massive amount of preparation before setting foot out of their homes? Because you obviously don't have a clue what you're on about. It's akin to suggesting that the people of eastern Germany are darker than those from western Germany. They're the same people. The border between North and South only went up roughly 70 years ago. There are plenty of farmers here in the South and older people who have spent their lives tilling fields who are darker than the people in K-Dramas. Use your head.
If you consider being forced to work outdoors all day as 'tan' versus spoiling oneself with quack skin whitening products then you're quite thick.
No... they are pretty very much harmoniously the same....
Depends on where in the country. It depends how long they stay in the sun working, like the farm.
probably cause god made them that way