Very interesting. Never seen a Japanese Kaisereich AAR.
Maybe after this is done you could help with the Japanese page on the KaiserWiki?
Its severly lacking.
A couple of thoughts.
Support the Entente.
With the Entente being the lesser of the three alliances, they quickly get thrown to the wayside. With a little bit of Japanese support, they could actually have a little bit of a say. Usually its just Germany v. Syndicates.
Ally with Mongolia
Is Manchuria your puppert in this scenario? If it is, a Mongolian ally would be most beneficial. You would have China almost completly surrounded and the Russian Far East would be in danger. Plus its better that Mongolians and not Japanese die against Russians.