>>518692720 (OP)
>Why can't Japan and China get along? Why are they always fighting with each other?
That requires an understanding spanning thousands of years.
China has always considered itself as the root of all civilization, which is where the "Middle Kingdom" terminology originates from. Middle is not the right word, because to the Chinese, they are the center of the universe and all of those around them only exist to serve China.
This is why China has attempted to conquer and subjugate its neighboring nations for thousands of years, Japan being one of them. The Japanese used to be known to be ruthless and vicious and China has a large part to play as to why that is the case. They have antagonized every neighbor and that's also why practically all Asians despise the Chinese, even if they descend from a Chinese lineage.