The Japanese have always seen somewhat contemptuous of Koreans, North and South, sort of the way a *sophisticated* New Yawker* might view an Ozark hillbilly, or a staid and formal Prussian look down his nose at his Bavarian cousins.
Except for one guy. A couple of years back there was an incident on a Japanese subway platform, and a Korean threw himself to certain death in front of a train to try and save a stranger, who as averages would have it, was Japanese. The result on Japanese society was far-reaching and profound, of the sort of national galvanization we felt here following JFK's assassination, or after the 09/11 plane hijackings and crashes.
That's not at all to say that Nippon is not indeed mightily pissed at NK for the kidnapping of its citizens. But expect the resoponse to be one that the Japanese have carefully considered and measured, rather than an instinctive and reflexive one.