They are better armed than you might think. They 've got a small blue water Navy, an Air Force that can easily reach North Korea, (Which includes F-15Js, E-767 AWACS, indigenously built fighters).
BTW, the South Koreans have F-15Ks, pretty much the same as USAF F-15E Strike Eagles, with LANTIRN precision targeting, navigation, and terrain following pods.
I'd be button popping if those -Ks took out Little Kim, since I worked on the design of the terrain following system, which would be very useful in the mountainous terrain of the Koreas.
The US Navy is so immensely vast that EVERYTHING else is "small" relative to it...
But in terms of modern ships the Japanese Navy is actually one of the largest in the world.