Kamikaze possibly don't take into account small conflicts that could arise ( as had been for thousand years already).In the case off small altercation with Noth Korea, they will strike beautiful Japan with conventional rocket to wide open all existing nuclear reactors.Long standing damage and amount of uranium particles released exceed one of biggest nuclear bomb.Japan wasn't able to protect itself from naughty ocean wave , so even less capable against NK threat.

Now Kamikuze could do computer simulation to see what percentage of land area will be covered with nuclear fallout in the case all power plant do release their content.
Typical nuclear reactor conform 100 tonnes of Uranium.
Now multiply that by amount of nuclear power plants in Japan - 42
Compare this to 60 tonnes released in Chernobyl disaster. I think that Kamikuze have already Plan B ( as the rest of Japan population) - migration to Australia safe heaven, when thing go really wrong with neighbour constantly poked into eye with stick.BTW New Zealand will even refuse entry to person so much irradiated as Kamikuze, US will not issue green card, so not so much places to hide for cocky, but naive