Japan is concerned with aggressive Chinese nationalism. It perceives China as a threat to its sovereignty. China on the other hand perceives Japan as the biggest obstacle in pursuing One China Policy, since Japan is in military alliance with the US, and with every passing geopolitical misadventure done by China, Japan is increasingly shifting towards the west.
China threatened the US with a high intensity showdown involving nuclear weapons if a COVID investigation is done.
Let’s assume that an investigation is carried out, and a showdown begins. Let’s see how China will lose the showdown.
Japan remained quiet for a long time but after the Wuhan Crisis, things took a turn. Japan and South Korea are the only two countries in the pacific region which are not indebted to China. They are western leaning countries too, with the US being their security provider, which makes China uncomfortable, because both these countries are in close proximity with China, so basically it's the US sitting so near to China.
Recently, Chinese officials suggested that they need to increase their nuclear capabilities against the US, so that the US comes to the table to talk, but what China is concerned about is that even in the case of war with the US, the US won’t be bringing war to its home.
How? Of course, because US bases are there in Japan, and in such a case, Japan will also be helping the US, so China won’t really be able to reach US’s Californian beaches. On the other hand, the US would destroy Shanghai’s skyscrapers, because it is situated near Japan. So while Chinese civilians will be involved in any kind of conflict, the US will be able to safeguard its citizens from direct burn of the war.
This makes China angry, and to have some edge in the conflict, it needs Taiwan. Taiwan is geo-strategically located and can be used as a buffer zone to stop the war coming to mainland China.
But Japan opposes it, because Taiwan is near Okinawa, an independent Taiwan can be the best geopolitical development of the millennium for Japan. Therefore, Japan has subtly started to disregard Taiwan as China’s territory in actions such as displaying Taiwan apart from China in the Tokyo Olympics map. Other instances where Japan has used Taiwan stability in its defense papers. This shows that Japan acknowledges Taiwan’s importance in case of any kind of hostility or ‘showdown’. This makes China frustrated and therefore the threats from China to nuke Japan over the Taiwan issue.
The long-standing dispute of the Senkaku islands had made one thing clear for Japan, its views on Chinese aggression.
Therefore Japan initiated SCRI (Supply Chain Resilience Initiative), along with India and Australia.
But as things started taking an ugly turn from the Chinese side, including giving rights to the coast guard to fire without provocation (January’s coast guard law), Japan quickly changed its military approach towards China.
Nobuo Kishi, the Japanese defense minister, urged European nations to help Japan combat China militarily in the region in the European security parliament.
Taiwan will be an issue which will drag the US and Japan against China in a war. Therefore, Japan also recognizes the role of India in the stability of the Indo-Pacific region.
China also has taken note of it and therefore launches military skirmishes with India so that India also does not get involved in Taiwan. This scheme seems to be working, but only until the ACSA agreement comes into play. The ACSA (Acquisition and Cross-Servicing Agreement) between India and Japan enables both countries to use each other's bases.
This means that Japan has an obligation to help India if the latter ever asks for it, and Japan likewise expects India to respond to any of its distress calls. This factor also irks China in that both of its rivals, India and the U.S., are in military agreements with Japan.