I know Japan has been building up their military but not fast enough in my opinion. If this doesn’t scare Japan into building a strong military nothing will.
Unfortunately, Japan's Constitution would have to be Amended to allow Her to build certain aspects of Her military.
This was a good thing after WWII, but I believe not so much now. I believe she learned her lesson and has been a good citizen of the World for many many decades. So, I say let her build her military, which could be astounding, and show North Korea what she can do.