Doubtful if the war would have happened then. Even with the Anglo-American support, Japanese struggled considerably in land war portion of the war. With trans-siberian railways fully connected, numerical advantage would have been overwhelming.
Japan linked the interest in the Manchuria and Korea in the series of negotiations prior to the war IOTL. Maybe division of the spheres of influence between Russia and Japan, with Russia taking Manchuria and Japan taking Korea could be amenable. Although with Russia at clear advantage, something like division of Korea at 39th parallels- around Pyongyang, I believe- would be also probable.
This would -ironically- probably going to prolong the independence of Korean Empire, with them taking positions similar to what Qajar Perisa took during the Great Game between Britain and Russia. Japan would certainly be more cautious and tries to enlist more support from the UK & US, while continuing the modernization. War could break out a decade later, with huge global geopolitical consequences.