Why are so many Koreans naturalized in China?

This is nothing to be surprised about. We have been adjacent for thousands of years. Look at North Korea arresting Americans and kidnapping Japanese. Do you think those are all acts against a certain country? Look at the faces of American spies or travel journalists and listen to their names: not all of them belong to an ancestor of North Korea, and think about the large number of North Koreans in Japan. . .