Sandy, I for one would not mind the NK extinction.
If Japan makes an air strike, a single blow will not do. They'll have to keep it going - blow up a target a week, terrorize the North Korean military until they can't sleep at night for fear of bombs.
Unlikely but necessary to follow up with a US land invasion to eliminate the regime for good. Preferably without prisoners.
"Mankind, when left to themselves, are unfit for their own government." - George Washington