Well there's that. Or if they lose badly, they can enter the dustbins of history like most of China's former enemies. China wasn't always this big. They just became this big because their enemies were annihilated of even having a proper identity.Japan yearns for decolonization and denazification. In ww2, they ironically projected their own mental colonization to claim they would free Asia from imperialism, when in truth, what was always needed was for Japan itself to be set straight and returned back to it's family.
All of Japan's traditional roots originate from the mainland. When they tried rejecting it in favor of aping the west, the results were laughable and turned them into a soulless nation.
China should use all means, diplomatic, economic and military, to recover Japan as its subject, which is the role that will benefit the Japanese people most in the long run.
For example if Russia wasn't strong, there would simply be no country named Mongolia now and Mongols will go the way of the Xiongnu.
Did you know Qingdao was once owned by Germany and Japan? No one really thinks much about it like let's say Hong Kong. Why is that? Because it was under China long enough to eliminate any German/Japanese traces from it except the beer.