South Korea and North Korea have been sworn enemies like "brothers" for decades. 1950, North Korea declared war and launched a unified offensive, and almost completely occupied South Korea in just a few months. After the intervention of the United Nations troops led by the United States, the border drawn by the two sides after World War II was finally maintained. Although the two sides stopped fighting, they did not sign a peace agreement. North Korea supported millions of troops and threatened the security of South Korea at all times. In the early 1990s, after the end of the Cold War, North Korea, which had long relied on the Eastern Group, was severely hit, its economy took a sharp turn for the worse, and its political power was in jeopardy every year due to serious natural disasters. This is a good opportunity for South Korea to complete the reunification of the peninsula or further weaken North Korea. South Korea has adopted a completely opposite strategy: to promote sunshine diplomacy and aid North Korea. Obviously, South Korea has a clear understanding of reunification. In particular, it learned the lessons of the reunification of Germany and Germany in the 1990s and paid a heavy economic price. With South Korea's economic strength, it is impossible to bear such a burden as North Korea. The pressure brought by the collapse of North Korea may even lead to the collapse of South Korea's economy. Therefore, it is better to hand over more than 20 million poor compatriots in North Korea to the Kim regime. Therefore, maintaining the status quo will naturally become South Korea's diplomatic first choice. Therefore, it is not surprising that South Korea will jump out to oppose the United States pushing North Korea too hard. In addition, South Korea is also worried that once the peninsula is unified, the United States will give up or at least reduce its support for South Korea, which South Korea does not want to see. Like Japan, South Korea is also worried that China, without American checks and balances, will dominate East Asia and even the whole Asian affairs.