I don't think Japan would have much control over what was happening out of Okinawa given a outbreak of war in Korea. Just as I don't believe the one or two nukes North Korea has are currently mated to a lauch vehicle that's ready to go from a launch site that isn't observable from satellite. A little planning might straighten that out, but as McGrath points out, there's no reason to believe that North Korea has been pushed that far yet. We'd have warning from the Chinese if something were up. Really.

I was responding to the question of whether the US was planning an invasion of North Korea. I've laid out the reasons I don't think that's likely, particularly given where our carriers are or rather where they aren't.

Here's the link so anyone can check for themselves:

Where are the Carriers?

Look for at least two carrier task forces on extended deployments off the Sea of Japan before anythink like an invasion of North Korea could happen. Defensive war from Okinawa? Yeah, sure. Offensive war from Okinawa? No way.