Its ironic that Japan says its strongly against N.Korea's nucleor program and many other things that the country does, but then certain members of its population are found trading with N.Korea in a way that could encourage the very things it says as a nation its thoroughly against N.Korea doing.
Personally, i'm against any trade with N.Korea, whether its related to its nuclear ambitions or not- to trade with such an immoral and corrupt country is to in one way or another lend support and more power to its government. People say they sympathize for the people of N.Korea and they say they won't do anything to lend support to their government which enslaves them, but then when faced with profit, the moral high ground is quickly put away and people turn a blind eye to the potential likely consequences of their actions of trade with such a country.
The more people trade with N.Korea, the more powerful it becomes and thus so its government also becomes, and the more powerful its government becomes the tighter it can pull the noose around its people's necks etc.