I never suggested otherwise. However, the OP explicitly asked for the destruction of Japan so as to prevent its rise in the future. Doing so entails an occupation, an occupation that would, as you yourself omitted, be impossible. Furthermore, these "raids" would undoubtedly cost the Russians more then the Japanese.
To do to Japan what Sherman did to the ante-bellum south is also impossible. Sherman was up against a relatively minuscule number of confederates, which allowed him to frequently divide his army in order to acquire supplies. Against the Japanese however, the Russians would not be able to employ this strategy. This isn't a repeat of the Opium wars, with a pre-industrial army getting slaughtered by a comparatively small industrial one. Rather, this is two modernized, industrial nations going up against one another. This era was defined and won by the number of men on the field. The Japanese, fighting on the home islands themselves, would be able to deploy as many men as they had guns. Thus, the Russians would be unable to break through and replicate Sherman's success at total war because they would be unable to periodically divide whatever army they manage to get onto the islands with a large Japanese presence looming over them.
To elaborate further, they cannot land chucks of the invasion force throughout numerous sections of the islands. They would simply get annihilated, one by one, by a larger combined Japanese force. So, that means they have to perform one massive landing and establish a beach-head. Knowing that they lacked the logistical capacity for such an undertaking, this scenario that you purpose is already rendered impossible. However, lets wave a magic wand and assume they get the bulk of the Russian army in the Far East onto one of the four islands. From there, they would then have to break out of the beachhead, which would entail defeating whatever combined army the Japanese manage to muster. After said army is defeated, only then can they pursue a strategy akin to Sherman's.
And all of that's assuming that the British, who have a very vested interest in containing Russia, reacting to the Russians invading, occupying, and dismantling their closest ally in the region with ¯\_(ツ)_/¯