Admittedly, the Chinese people have historical reasons for antipathy toward Japan. Not excusing Chinese aggression now, but there's a lot of hate over there to go around.
And ‘historically’ the Japanese have reason for antipathy for the Chinese given two invasions of the islands previously. Anywhere there is a border between linguistic, social, or political groups in the world there is a history of some level of conflict....always has been....always will be.
One who studies history would know it goes both ways. There's about 1500 years of bad blood between the Chinese mainland and Japan, in ancient wars. Attacking hordes from China would kidnap Japanese women and tie them to the outside of their boats to humiliate the Japanese. The Japanese got over it regarding old wounds. Not so with the Chinese, because WWII is still fresh in living memory.