Isn't the in-between choice to drive or fly out of Russia towards Europe, then fly east on a non-Russian airline, and eventually take e.g. the Tokyo to Vladivostok direct flight?
The Russian airlines can't fly to most of Europe. They're sanctioned by the EU. You'd need to drive. But better option is probably just flying through Turkey. Turkish Airlines still operate in Russia. Turkish Airlines isn't sanctioned, so they can maintain their planes just fine.
This isn't _that_ relevant because China is there as an option but there are no flights direct from Japan to Russia, for the same reason there aren't EU to Russia flights right now either.
