Japan's swimmers and officials earlier refused to get drawn into a political row at the Asian Games. The team's head coach said there had been "no signs of agitation or annoyance" at Sun's remarks.
"About the anthem, I'm sorry that some media reported that," Olympic champion Sun told reporters after defending his 1,500 metres freestyle title.
"Maybe there was some misunderstanding about that. I don't really know about other countries anthems," he added. "But every swimmer wants to listen to their own national anthem."
Japan and China are fierce political and sporting rivals with disputes over territory and their history to sort out.
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"It is a very delicate issue and we didn't hear what he said directly so it's difficult to comment, but what is fact is that there is no agitation or signs of the swimmers being upset," Umchara said.
"We have come here to swim and the athletes do not get involved in issues beyond swimming. The (Japanese) swimmers who interact with Sun and know his personality have decided that there wasn't any malice in what was said."
"Sun Yang is not the only swimmer to say things on the spur of the moment," said Umehara.
"We are here to fight for medals and you have to be up for the battle. But we have instructed our athletes about the importance of sportsmanship and respect.
"Sportsmanship might mean different things in other countries but clearly anything touching on the subject of the national anthem is a delicate and difficult issue.