The first version I heard of, was a book published by a Christian organization in the USA that, based on the claims of one American correspondent, an anonymous Kempetei or Intelligence officer and discredited(by Japanese, Korean and Chinese TV specials) ousted Japanese scientist...the first version of the story back in the 90s was 1 bomb successfully tested and witnessed by thousands of Manchurians in Manchukuo in 1943...the second in Korea in late 1944.

The next version of the story was 1 in Manchukuo in 1944 another Korea 1945.

There was an actual TV documentary done and shown on TV to counter the Hiroshima memorial day, which may be telling about the producers...was 1 successfully detonated on the Korean coast before the American bombs dropped and even a 2nd in Japan itself in the far north by the navy program(the navy and army had 2 separate untied uncooperative programs going).

They claim that it was the Emperor or PM who chose not to retaliate though they could.

They also claim that the reason the Chinese and Koreans side with the Japanese as this being more American propaganda(and those 2 are the least likely to defend Japan about ww2) is that Russian occupation forces removed all the factories, materials even tools and somehow cleaned up the radiation too.

Critics have so much to point out I can't go into it.
But here are 2.
a) it meant that the Japanese had figured out a way hundreds of times more cost and time efficient than the Manhatten Project
AND that to this day they refuse to use that knowledge even for their own nuclear power programs.
b) if the Russians did kidnap(including staff) a successful Japanese atomic bomb program they would have had their own by 1946.

But who knows?
to this day most Americans believe the Spanish torpedoed the warship Maine in Cuba.

Most still believe Saddam was behind 9/11.

According to their recent Presidential coverage, nearly 40% believe the universe is less than 6,000 years old...

despite the fact that even Jimmy Carter, who used to be involved in physics notes that if you believed that you'd never have mastered the science to create the atom bomb.

And we think the Japanese, Germans and Italians were the only ones to swallow propaganda?