While the Chinese reaction to the Japanese announcements does seem oddly disproportionate at a glance, one needs to understand that the Chinese government is not immune to the whims of Chinese public opinion.
While the Chinese public has an admirable degree of maturity and patience when it comes to Trump’s various antics, the Japanese have deservedly earned a position of deep and fierce animality if not outright hatred in the hearts of the overwhelming majority of the Chinese public. Especially the unrepentant, revisionist fascist ones.
This is indeed an area of emotional vulnerability for China, in that it would be relatively easy to bait China into war using Japan, as China’s collective tolerance for any sort of bullshittary from them is outstandingly low.
This is why Chinese naval modernisation especially have focused so heavily in given Beijing the tools necessary to not only repel any hostility from Japan, but more importantly, to take the fight right to their home islands. And I’m not talking about just bombs and missiles, but actual boots on the ground full force invasion.
If you think about it from a purely risk-reward standpoint, it actually makes relatively little difference if it was a Taiwan AR scenario that led to Japanese military intervention and Chinese full force retaliation that culminated in the invasion of the Japanese home islands; or if a full scale war between China and Japan and/or America that led to Taiwan declaring independence and triggering AR.
However, a China-Japan war does offer unique opportunities to both call America’s bluff, especially under TACO Trump, and also unlock a real possibility of a peaceful reunification if the PLA’s demonstration of its true combat capabilities coupled with America’s chickening out shattered all hope and illusions that Taiwan could ever hope to achieve independence.
Let’s be clear, I do not think this current round of tensions is China preparing for such a war. Rather, I think it’s China demonstrating to Japan as clearly and explicitly as China ever will that it is fully ready to go to war with Japan directly if it ever tries to threaten to use military force against China, and that any such war won’t just be a short skirmish.