Will Yoon's exit change South Korea's US-China approach? / Japan hosts China, South Korea foreign ministers / Chinese and South Korean foreign ministers hold first call since Seoul martial law crisis / South Korea's tumult is a symptom of China-US strife / China-South Korea ties: empty ambassador chair highlights complications in relationship / Chinese senior officials' South Korea trip to coincide with Putin's Pyongyang visit / South Korea's top diplomat to visit China ahead of much-awaited summit with Japan / South Korea's China ambassador faces abuse probe as President Yoon gets no respite after election rout