One thing that people unfamiliar with Korean culture (and several Asian cultures in general) might be surprised to see upon their first visit is the site of women holding hands together as they walk down the street. It is a sign of friendship, and nothing romantic. You can commonly see it not just among school-aged girls but even middle-aged women or older as well.
It can be a bit more challenging in some respects to get candid shots of people in North Korea. Mostly this is because while more and more common, the sight of foreigners is still a bit unique in what is one of the most homogenous societies in the world. North Korea is comprised of 99.998% ethnic Koreans, and so if you're living in North Korea and see a non-Korean, it's going to catch your eye, diminishing the candidness of the moment.