Tension at the China, Russia, and North Korea Tripoint
The simplest way to describe the relationship between China, Russia, and North Korea is complex. This relationship is reflected in the border: almost 1000 North Korean defectors try to escape through China or Russia every year, and yet both states have a policy to immediately deport any defectors back to North Korea for punishment. There is only a single bridge between Russia and North Korea, which doesn't even see traffic every day. Only authorized trains and vehicles may cross. Chinese tourists may travel to North Korea, but only to certain areas and under heavy surveillance.
During the 1800s, the Korean peninsula was controlled by the Qing Dynasty of China. The Russian-Chinese border was then established by the Convention of Peking in 1860 to be the Tumen river. Then in 1910, Imperial Japan took over the Korea until 1945. In 1951, the only bridge between Russia and North Korea was built. The Border between North Korea and Russia has not changed since then.
The modern China/North Korea border has largely been the same since the 15th century, running along the Tumen river in the east, then the Yalu river shortly after the Tumen ends.
In summation, there's not too many people living on the tripoint today, but how these few people interact is very important in International Politics. Which side of a small river you were born on can determine what language you speak, how much food you have to eat, and how much autonomy you have. Those living in Tumen, China; Namjungsan, North Korea; or Khasan, Russia live very opposing lifestyles. For many people in the world, a border might not mean much for the way they live their life, but for these people it represents a hard ideological separation.