Japan doesn't have nuclear weapons currently, there are many Japanese who feel they should but many don't want it. If an outside force tries to remove their institution no matter the reason then very quickly China will have a "Ukraine problem" on its doorstep. This has ripple effects and other neighbors will take measures that will make life difficult for China. If China decides to get into adventurism, it will have to drain resources maintaining it and we can see the folly in this system.
It's one thing if Japan re-militarizes and attacked China tomorrow, any action would be understandable. It's another thing to use 20th century grievances to remove an institution that has lasted centuries. China has become a super power and outclasses Japan, their emperor is a gloried mascot, Japan will not invade China because their leadership understand the stupidity in that so what's the rah-rah about destroying their cultural institution? You don't have to make me understand injustice, I understand the humiliation that comes with colonization. My people were subjected to the worst form of chattel slavery, brutal colonization and near genocide by outsiders. Blacks had to march just to be treated like human beings and given the right to vote as recently as the 1960s, so I know all about the feeling.