Japan can build nukes at a drop of the hat, but then Taiwan and S. Korea will want them too. S. Korea can do it probably now. Taiwan could if they wanted. China will wig out about that of course. We need to stop N. Korea before it gets out of control. They have had 50 years to get rid of this thug and his dad, they might need to be collateral damage. Stone age em.
At this point I don't see why Taiwain doesn't build nukes. Better than letting the China invade and doesn't look like anyone else is going to help them if China gets aggressive (which it will eventually).
I suspect Taiwan has plenty of them, and wouldn't be at all surprised if SK does too. There's far too much incentive for both countries to have them, for it to be otherwise. Their ace in the hole, however, is to keep their existence a secret -- so I suspect we won't hear about them.