Sounds like China would prefer to deal with a nuclear-armed Japan (as opposed to a nuclear-within-a-month-has-all-the-knowledge_but-no-arsenal Japan).
A basic Toyoda has more high tech than a nuke.
Also the Japanese have >9 tons of plutonium in stock.
And just for fun they want to reopen their reprocessing plant.
Or nuked-up by the time you finish reading this post. They probably have all the components built, tested and sitting no further than 6" apart from each other awaiting assembly orders, and has probably had them there for decades.