The Japanese are roundly hated in most of Asia. I have close friends who are from Hong Kong and they can barely mention Japan without some sort of negative comment.
Asians tend to be racist...period. Regardless of their race, they tend to hate those who are not their race. It's not just Japan and China.
It is just human nature for them to suspect the Japanese have not changed. When I moved from Maryland to Texas in the 70's I caught a bit of how Southerners still felt about 'Yankees'. (I know Maryland was not really a Northern state, but they were cowed into serving as Union soldiers).