OF1 - exactly. I recall a RUSI paper a few years ago looking at nuclear proliferation and the concern was that Japan would be next. Strategically if could argue it needs them; it have the launch vehicles for IRBMs, it has the nuclear industry and the infrastructure. At the moment the UK processes its spent fuel, part of a cunning plan to deprive Japan of the key ingredient.
But the Japanese public are still a bit iffy about nukes. God knows why. It was 69 1/2 years ago...