Oscar-winning animator Hayao Miyazaki, whose last film was accused by some South Koreans of glamourising war, said Monday Japan needed to clearly state its remorse over its imperialist past.
Miyazaki, a well-known liberal, said Prime Minister Shinzo Abe needed to be explicit in his condemnation of 20th century warring.
"I think (Japan) has to say clearly that aggressive war was completely wrong, having brought enormous damage to the Chinese people," he told reporters at a rare press conference in his Tokyo studio.
"Regardless of the political situation, Japan has to have deep remorse over a long period of militarist activities in China," he said.
Nationalist Abe is readying a statement to mark the 70th anniversary of the end of World War II.
He has repeatedly talked of the need for what he calls a "forward-looking attitude" that concentrates on the positive role Japan has played since surrender and continues to play.
But that has set alarm bells ringing in Seoul and in Beijing, which say any attempt to tone down explicit apologies made by previous prime ministers should be discouraged.
"I know there are many people who want to forget about it, but it never should be forgotten," Miyazaki said.
The comments come two years after the release of his final feature-length film, which was praised for its artistry, but criticised for what a minority of people said was romanticisation of conflict.
The film, entitled "The Wind Rises" in English, told the story of a fighter plane designer modelled on flight engineer Jiro Horikoshi, the man responsible for the Zero fighter, Japan's best known World War II fighter aircraft.
Miyazaki has responded to the criticism reportedly saying "Horikoshi was a person who has resisted requests from the military. I doubt he is blamed just because he lived a life at that era."