Ra, theres a FERRY that runs for 10 minutes from the tip of Japan to South Korea... just under the border with NK. Not to mention warships, transports, etc.
Dutch, you cannot possible believe your government will just allow NK to lob a missile and hit one of your cities and just "let it be". You fellas are not in an Israel-like situation; if you get hit, the only ones getting in deep **** are those that lobbed the missile. And the JDF is not a "defensive" force, its an actual military with full offensive capabilities; they are only limited by the constitution. True, it is not as large or as radically massively armed as the US, UK or Australia, a "defense force" cant be justified if its big. But you can bet your arse the JDF is ready to perform any offensive action it may be called upon.
I dont mean to tell you how things are in your own country, far from it! All i'm trying to say is one thing is what is advertised for the benefit of the public (including international public) and another is cold, logical reality. No military ever exists without it having contingency plans for offensive operations, the JDF is no different, and given its purpose and the reason for which it was created, its virtually guaranteed they are ready to go out and kick arse.