South Korea and China have made remarkable progress in their economic, cultural and social relations since the opening of their diplomatic ties 22 years ago, with their trade volume, bilateral tourism and people-to-people exchanges on a steady rise.
But uncertainty lingers over how the relationship between the former Cold War foes will evolve amid shifts in the regional security landscape that were triggered mainly by China's reemergence as a major power in the Asia-Pacific.
Geostrategic and security issues such as North Korea's nuclear adventurism and the intensifying rivalry between the US and China are expected to affect the future direction of the Sino-South Korea relationship, analysts say.
"How the Sino-US relations will develop, how South Korea and China will respond to North Korea's nuclear saber-rattling, and how the territorial feud between Beijing and Tokyo will unfold ... All these crucial variables will impact the relations between the South and China," said Kim Heung-kyu, a China expert at Ajou University.
"Thus, uncertainties over the future of the relations remain very high. China has recently been showing its intentions to foster a new China-led Eurasian order. It is uncertain how South Korea will be treated in that process of building a new order. Many challenges could lie ahead for Seoul."
Since the start of the Park Geun-hye administration in 2013, China has been atop its foreign policy priority list. President Park has sought to strengthen Seoul's strategic partnership with Beijing, which had been stunted by the former government that focused mainly on its relations with the US
Since their respective inaugurations less than two years ago, Park and Chinese President Xi Jinping have so far met five times for summit talks, which have highlighted the close relationship between the leaders. Xi has yet to meet Kim Jong-un, the leader of North Korea, a country that former Chinese leaders had pampered with economic and political support.
The two leaders have also put up a united front against Japan's lack of atonement for its wartime misdeeds including its sexual enslavement of Asian women at frontline military brothels, and against what they call Tokyo's distortion of history in school textbooks.
On the issue of Pyongyang's nuclear ambitions, the two have been on the same wavelength, presenting their strong opposition to the reclusive state's development and possession of nuclear arms.
But the deepening ties between South Korea and China have posed a diplomatic challenge to Seoul as Washington is concerned that its pursuit of a three-way security collaboration with South Korea and Japan could go awry.
China's recent moves to foster a new financial and security order in the region are also expected to pose tricky policy challenges for the South, which relies heavily on security cooperation with the US to counter North Korean threats.
China has recently sought to build a new regional security architecture and set up the Asian Infrastructure Investment Bank, both of which would exclude the participation of the US and other Western powers. These moves appear aimed at laying the foundation for China's regional dominance, some observers say.
During their summit last month, Xi requested that Seoul join the AIIB. Washington had reportedly urged Seoul not to join the bank, which Western critics suspect could be a tool for challenging existing institutions such as the Asia Development Bank that have been dominated by Western states and Japan.
Amid China's efforts to court the South, the US has apparently been upping pressure on the South to support its "rebalancing policy" toward the Asia-Pacific, which China sees as intended to counter its rise.
As part of the policy, the US has been bolstering its military presence and expressed its wish to deploy to Korea an advanced missile defence system, called the Theater High Altitude Area Defence, to better counter the North's missile threats.
China has shown opposition to the deployment of THAAD as its radar system ― with a maximum detection range of some 1,800 km ― would cover China as well.
Analysts say that South Korea should craft a more creative, prudent diplomatic strategy to maintain healthy relations with China, an increasingly crucial partner for trade, tourism and efforts to denuclearize the North, though external diplomatic variables may prove difficult to handle.
Under former President Roh Tae-woo's foreign policy initiative, dubbed "Nordpolitik" ― German for northern policy ― Seoul established diplomatic relations with Beijing in 1992 after severing ties with Taiwan.
Their economic relationship has thrived, satisfying the needs of both countries. For the South, China's huge market has offered new opportunities for economic growth.
For China, Korea's technology has been helpful for its industrialization. The opening of ties with Korea also helped it escape from the international isolation that resulted from its bloody crackdown in 1989 on pro-democracy protesters at Tiananmen Square.
The two countries elevated their relationship to a "strategic partnership" in 2008, leading to an increase in high-level contacts. During the summit last month, the two leaders agreed to forge a "mature" strategic partnership through expanding their cooperation in various areas.