By framing it like this, it also leaves the door wide open for Russia to join the party as another successor state to one of the original WWII principle victors.
While some might scoff at what the Russia military might bring to the table, but geography alone means it can make a massively powerful contribution. As well as the political and diplomatic benefits of having another great power second China’s position.
Russia gains from potentially finally getting somewhere for a naval base that isn’t frozen over half the time and isn’t easily bottled up. As well as weapons and industrial support from China, which it can redirect to Ukraine if thats still not won by then.
Frankly speaking, should China go into war with Japan over Operation AR and/or the Ryukyus (and the US and its Lackeys Co.), personally I don't think Russia needs to join the conflict as an active belligerent.
The Russian Navy's Pacific Fleet based at Vladivostok and Petropavlovsk-Kamchatsky could serve as mobile fleet-in-beings by tying up certain portions of the JMSDF and the US Navy forces in the Northern Pacific, primarily with their SSNs and SSGNs (alongside their SSBNs and SSKs to a lesser extent). The Russian Long Range Aviation bomber fleet that is based at Ukrainka would be a useful addition to this combo as well.
In addition, the airspaces around the China–North Korea–Russia border tripoint could be utilized for PLAAF warplanes to transit between Northeastern China and the Sea of Japan for missions targetting the Japanese home islands. Similar arrangements could also be made for airspaces above certain parts of the Russian Far East that would enable PLAAF warplanes to conduct missions in the Northern Pacific.
Moreover, without active participation in the war, Russian military assets cannot be legally attacked by the opposing forces, as long as they stay just beyond the reaches of the active combat regions during the war. This should be useful for collecting military intelligence, which could be passed onto the Chinese side.
The same applies with North Korea.
