Just recently, North Korea launched a ballistic missile into the Sea of Japan. It may suggest an opposition of the North to the meeting of China's leader Xi Jinping and Donald Trump.
Soon after that, South Korea was also reported to have tested an 800km-range missile. This ballistic missile can target Pyongyang from anywhere in the South.
The Guardian: South Korea test fires 800km-range missile
South Korea has been relying on the power of the US to protect itself from the threat of North Korea. Since 2012. But, South Korea and the US have made an agreement about the development of long-range missile weapon.
Donald Trump, President of the US, is reluctant to keep the troop on duty in South Korea. He suggests South Korea should compensate for its cost.
On the other hand, the US was eager to set Terminal High Altitude Area Defense missile (THAAD), a high functioning system for countering airstrikes, in South Korea. As deciding to adopt THAAD, South Korea was harshly blamed by China. China seems to be afraid that THAAD would prevent it from attacking the US. Even though it is unlikely to occur, an option to begin a deliberate attack must be a trump for China when negotiating with the US.
Therefore, South Korea is forced to become solitude in the international power balance. As President Park was dismissed, which direction it will proceed to is quite unclear.
Anyway, the situation around North Korea has become more tense. I expect leaders in each nation to be rational with a longitudinal perspective.