"The more rapid the growth is, the more dangerous I think it is going to be for nationalism to play a role or change the course of the ... nation," said Tomohiko Taniguchi, deputy press secretary of the Japanese foreign ministry.
"I would call on the Beijing government to well manage the equilibrium of the Chinese psyche, because the Chinese people are experiencing the most rapid ... change in their 2,000-year history," he said at a press conference in Hong Kong, where he was attending a cultural cooperation conference.
China and Japan have feuded over the extent of Japanese brutality during its occupation of China during the World War II era.
Among the Japanese atrocities that have flared Sino-Japanese relations, historians generally agree the Japanese army slaughtered at least 150,000 civilians and raped tens of thousands of women in Nanjing in 1937.
Historians also say as many as 200,000 women, mainly from Korea, China and the Philippines, worked in Japanese military brothels in the 1930s and '40s. Many victims say they were forced to work as sex slaves by military authorities and were held against their will.
Demonstrators vandalized Japanese shops and smashed windows at Japanese diplomatic offices in Shanghai and Beijing in April 2005 to protest the alleged whitewashing of atrocities in Japanese textbooks.
Meanwhile, many Japanese conservatives are disgruntled over what they say are exaggerated stories of Japanese brutality.
Taniguchi said Chinese youth are enjoying Japanese pop culture even as they express hatred toward Japan.
He said "nasty" anti-China feelings are also prevalent among Japanese youth, but called such sentiment a "reactionary" response to Chinese hostility.
The Chinese foreign ministry didn't have immediate comment on Taniguchi's remarks.