Relationships between all three neighbours are heavily coloured by history, while both Beijing and Seoul are embroiled in separate territorial rows with Tokyo over disputed islands.
The latest flashpoint between them is Ahn Jung-Geun, who shot and killed Hirobumi Ito, then Japan's top official in Korea, at the railway station in Harbin in northeast China in 1909.
Ahn, a Korean nationalist, killed Ito in response to Japan's colonial designs over the Korean peninsula where its influence had been growing.
Japan already held territory in mainland China at the time and went on to invade Manchuria in the 1930s before occupying most of eastern China during the war.
South Korean President Park Geun-Hye met China's top foreign policy official Yang Jiechi yesterday. Both said work was progressing on a monument in Harbin to Ahn, according to a statement by the presidential Blue House in Seoul.
"Ahn Jung-Geun is a very famous anti-Japanese fighter in history," Beijing's foreign ministry spokesman Hong Lei said at a regular briefing yesterday. "He is respected by the Chinese people as well."
Ito, Japan's first prime minister, was one of the most significant figures in the country's modern politics and Tokyo vehemently opposes the monument.
"We have been telling the South Korean government that Ahn Jung-Geun was a criminal," Chief Cabinet Secretary Yoshihide Suga, the government's top spokesman, told reporters today.
