I am actually surprised there is a small (tiny?) but still surprising number of people that feel Japan is a real, direct, short-to-medium term military threat to Korea, as in the shooting war kind. This is a sentiment I see a lot in the Korea subreddit, but that might just be overly "nationalistic" "Koreaboos" - who may even be mostly Korean-Americans that have rarely set foot in Korea, or not even ethnically Korean.

The sentiment is not non-existent in Korea itself too though. In fact, in some discussions of recent military developments by the RoK (plans for a aircraft carrier, SLBMs, F-35 and/or KF-X fighters, etc.) it's often touted by these folks that they are just as meant to be pointed towards Japan as they are to North Korea or China.