The Chinese never got past the Japanese atrocities in Nanking. And of course, Japan refuses to apologize (not that it would make much difference in my opinion). China is biding it's time. They have every intention of taking vengeance on Japan for what they did.
If I was living in Japan right now, I would be VERY nervous.
Actually, the Japanese have apologized dozens of times. But the Chinese have repeatedly questioned the sincerity of these apologies, typically linking the degree of sincerity to Japan's willingness to send more monetary reparations to China. Japan has spent tens of billions of dollars in direct and indirect reparations. But China has never acknowledged them as sincere enough. I think the Japanese are at the point where they're done apologizing, and aptly so. Chinese empire-builders have, in their time, carried out atrocities every bit as brutal as the Japanese, for thousands of years. The only difference is that the Japanese carried them out in the 20th century. Note that the Rape of Nanking is only one of perhaps half a dozen such sackings (involving large-scale massacres) in Nanking. The previous ones involved Chinese contenders competing for the throne.
While they have every reason to be pissed off at the Japanese, they have 4X-6X the reasons to be pissed off at their Red leasdership.
But their government doesn't let them talk about that, I presume.
Long ago, we had a Japanese-American as part of a deployment team to Korea.
He didn't like it but he always had two others with him except when we were working directly with counterparts.
(And he had in-laws in Seoul)
The Japanese probably get along with westerners much better than with other Asians - and they can be prickly over here.
And, a note to another FR'pr, japan took to western technology WAY faster than any other Asian state:
Think Russo-Japanese war.
A Chinese friend of mine tells me that the Chinese will absolutely never forgive the Japanese. Of course, I guess that means the majority of Chinese are still non-Christian.