No need. As others have posted already, Japan could become a strategic nuclear country within a *very* short time span. They have all the technological components, and know how, especially in the industrial machining equipment that would be required to shape the detonation assembly. They've had nuclear power plants for quite some time, and therefore should have a ready supply of nuclear material they can enrich to weapons grade. I'm sure that centrifuges wouldn't be a problem with their manufacturing capacity and prowess.
I do feel Japan needs to be re-militarized. I think the old ways are long gone, and, it's time that new Japan takes its rightful place in the world order. A second largest economy with almost no military presence ? That's a tad geopolitically untenable, to say the least.
It was, like the former PM said, because they sat comfortably under our umbrella.
So let me get this straight.
Japan as a sovereign nation can develop a nuclear weapon, but Iran as a sovereign state cannot?
Just playing the devil.