I assume you're going off the 1.365M + 1.2M combatant strength listed in the Wikipedia article?
Those are figures for the total size of those national armies at the time. It'd be like saying the Iran war involved 3M people because the U.S. has about 2.1M in uniform and Iran has just under 1M counting reservists. Meanwhile there've been precisely zero boots on the ground in Iran, and the total number of military personnel directly affected is on the order of tens of thousands.
The text of the article has the Russian far east strength at about 95,000 at the start of the war, with another 410,000 trained in over the course of the war. The best proxy for Japanese (and Russian) combat strength might be the Battle of Mukden [1], which had about 250K Japanese and 292K Russian troops. These numbers are smaller by a factor of about 5x.
The present-day Russo-Ukrainian war is significantly larger. Estimated Russian deaths are 500K+, higher than the total number of Russian soldiers involved in the Russo-Japanese war.
[1] https://en.wikipedia.org/wiki/Battle_of_Mukden