Japan is a signatory of the NPT. Japan is considered a a de facto nuclear state since we have the imminent ability to produce nuclear weapons and we already have the deliver mechanisms.
While there are currently no known plans in Japan to produce nuclear weapons, it has been argued Japan has the technology, raw materials, and the capital to produce nuclear weapons within one year if necessary, and many analysts consider it a
de dacto nuclear state for this reason. For this reason Japan is often said to be a "screwdriver's turn" away from possessing nuclear weapons, or to possess a "bomb in the basement".
In as less as 6 months Japan can produce a strategic weapon. With enough material to produce over 1000 warheads, enough to glass the entire planet.
But we won't. Simply because we value peace and are NPT members. I hope this remains so.
South Sudan. Come on man, the country is one of the poorest in Africa. They should focus on food development or water rather than nuclear weapons.
Beyond their scope.