[lvlrsSTI]

Japan has no effective means to attack Russia with or without US direct involvement. The Japanese archipelago & glass cities are extremely vulnerable and difficult to defend 

The military exercise in Russia's Far East is to show the West that Russian forces are logistically ready to defend the vast Russian hinterland from the East to the West, it is not bogged down by the ongoing operations in Ukraine

Japan wants to take back the 4 islands lost to Russia after the war.