It’s not well publicized and when it is its routinely dismissed. However, Japan did have a bomb research program. That program’s “Oppenheimer” - Bunsaku Arakatsu, was interviewed before his death about the program and somewhat reluctantly verified the program. There was a History Channel TV episode on this. According to a book (I will provide the link to Amazon for it!) written about the program Japan was 18 months from a bomb. The “physical plant” part of the program was in what is now North Korea. This was seized by the Soviets and copied or transported back and made part of their program. Some claim that there was a “Trinity-style” test done on a north Korean island with results varying from successful to “fizzle” - maybe planned and more of a “dirty bomb” then fission bomb. The author of the book in a new edition (see link below) claims the “physical plant” formed something of the basis of the NK program.
Note it’s been in the best interests of the left both in the West (the US particularly!) and Japan to deny all evidence of the existence of the Japanese nuclear bomb program. It allows the constant moral castigation of the US for being the first to sue the bomb and those promoting it opportunities to preen about their moral superiority.
The link
How I wish you could go back and correct typos!
Typo
“use” = “sue”
If I’m not mistaken the Japanese also had radar by 1945, for all the good it did them.