The three-day joint exercise that started this morning south of Tokyo brought together coastguard members who sometimes play cat and mouse at sea near disputed islands in the East China Sea.
The joint drills, which were being held in Japan for the first time, were hosted by Russia last year and South Korea in 2012.
The annual exercises usually involve six nations, also including South Korea and Canada.
Tokyo nationalised the disputed islands nearly two years ago, setting off a diplomatic row with Beijing, although the two countries still occasionally work together on similar exercises.
Japan highlighted the growing tensions in its annual defence paper today, saying Beijing's "dangerous acts" over territorial claims could lead to "unintended consequences" in the region, as fears grow of a potential military clash.
