China released three Japanese citizens on Thursday whose detention had added to tensions between Asia's two top economies, but a fourth remains in custody in a sign that the row is not yet over. Tokyo and Beijing have been in a bitter feud since Japan detained a Chinese fishing boat skipper whose trawler collided this month with two Japanese Coast Guard ships near uninhabited islands in the East China Sea that both sides claim. "It looks like the Chinese side is letting the heat out of the argument," said Phil Deans, a professor of international affairs at Temple University, Japan Campus. "It's not going to go away. It's very easy to reignite ... There is still a dispute (over the islands) and there are some very passionate figures on both sides that don't want a good relationship."