Japan is worried about North Korea

Japan is clearly worried about a North Korean missile attack. This article describes a significant policy shift on the part of Japan for dealing with North Korea. The Japanese Defense Ministry is apparently trying to change Japan's "defense only" policy. They are trying to make it so that Japan can launch a pre-emptive missile attack on North Korea. This, along with the previously mentionned story about the U.S. destroyer, shows that Japan is clearly worried and maybe they know something we don't. It's easy for us to say, "North Korea won't attack Japan" but for the Japanese it seems a very real threat and they, not us, are in danger. Do you think that Japan is being overly cautious or does it have a legitimate reason for doing so.