Most of the times I send Russian diplomats to Japan and ask an audience, they almost always declare war on the CP on the first turn... but under control as Russia.
Isn't it a bit odd? After all, Russia was one of the main threats to Japan's security, and vice-versa. They should be the least likely to bring Japan into the fold against Germany. After all, they did scrap two-thirds of the Russian fleet and humiliate them in face of the whole world...
I have no problem with them joining the Entente if France and Britain woos them out of neutrality, but there should be a huge malus against Russian diplomats in Japan.