And if Putin's Russia is just too nuts and aggressive to make such a deal, could Japan make secret deals with regional rulers of Russia's Far East to sit out a war between Japan and China and not allow Putin to use military assets in the region to help China?
There were always rumors during the Cold War about whether the USSR's Warsaw Pact allies might sit out a war with NATO rather than enthusiastically participate in an invasion.
Maybe Russians in the Far East see few benefits for staying in Russia and lots of potential problems being dragged along for Putin's viking funeral ride:
As Russia strives to reassemble its empire, first with bits of Georgia in 2008 and now with larger bits of Ukraine, several even larger bits of Russia want to secede, or at least become more independent. Several parts of Siberia have expressed an interest, often in the form of large street demonstrations, for this.
Interestingly enough, Strategypage also writes that Russia's Kaliningrad enclave is looking longingly at Germany.
Russia's Far East is far from Moscow and staying neutral might be the best way to avoid the repercussions of being dragged into a war by a distant Kremlin that doesn't have to live with the problems that will follow for those who live in the Far East.