>>14287981Except that they totally could on sea. Their navy is, not just in numbers but also technology wise very impressive.
Japan also has a pretty decent air force, the F-2 is one of the most modern planes in the world and probably the most modern F-16.
Generally speaking, Russia would have to invade an island which is guarded by a great navy and capable air force. Not to mention that Japan is essentially made for defensive action.
The US would support Japan anyways so air superiority will always be on Japan's/America's side.