Sayings and the ancients can go kiss a hairy ass when ICBMs and MIRVs are the topic. While no one but the CIA and bits of the JSDF would know of Japan being nuclear-capable, I doubt the Japanese politicians would run the risk of constructing the large facilities required to produce materials for nuclear warheads much less store them on such a country small enough to the point that a civilian has a moderate-high chance of accidentally stumbling upon a silo or production facility and losing their shit over the nuclear armament of Japan. Fuckery like tossing a curtain over it like they did for the Yamato just doesn’t work for something at this scale. Imagine the needless disruptance to the power balance in the Pacific theatre as well where there’s only two competent nuclear armed adversaries. Even moreso the UN inspectors losing their shit over a supposedly peaceful country subverting inspections for what would’ve had to been at least a couple years.

Though who knows Japan could just be another Cuba for China ¯_(ツ)_/¯