As always, I think Russia will survive someone not liking it.
I liken Japanese behaviour in the territorial dispute with the Chinese burning Japanese flags in the past (It has stopped now). The Japanese continue to mark the day of the Northern territories shouting abuse and threats towards Russia. Unlike Koreans or Chinese Russians don't have this type of demonstrations against the Japanese. Overall, the population is friendly towards Japan and Japanese but you should take into account that the public opinion is against returning the islands. Many consider this is a small price for the atrocities in Asia and for the Russian and Chinese soldiers who died in Manchuria. Anyway, even if any Russian president wanted to return some or all islands, it may not be easy and even impossible and the Japanese politicians shouldn't promise anything. There are two sides in any arguments
Marking Victory Over Japan in Russia is to commemorate the soldiers who died, they have been neglected for a long time. This is not against Japan. Russia also marks Victory over Germany but relations between Russia and Germany are very good on all levels.