Yes, but I'm not talking only about Japan vs NK. Japan should generally build some serious armed forces. They can't forever stay under US wings.
There is no use of you & me talking about it!!The Japanese government & people have to take the plunge & shape a new destiny for themselves.
PS-I read in a newspaper article about 6-7 years back that India,Israel & Japan were 3 countries which could build a functioning nuclear triad including submarine launched missiles & even ICBMs in a matter of few years given the highly advanced state of their civilian space & nuclear programmes.Israel & India have more or less reached there-no sign of Japan wanting to reach there.