This is mostly untrue. Most of this narrative comes from Soviet propaganda that was later propagated by anti-Western and anti-war groups in the United States. More recently, it's gotten more attention as Vladimir Putin and Vladimir Rudolfovich Solovyov use it as a useful tool to build their narrative that only Russia was responsible for World War II's victory and to justify their constant threats of nuclear warfare.

The historical record is very clear, as is Hirohito's own statement at the time:

"Furthermore, the enemy has begun to employ a new and cruel bomb, causing immense and indiscriminate destruction, the extent of which is beyond all estimation. Should we continue to fight, not only would it result in the ultimate collapse and obliteration of the Japanese nation, but it would also lead to the total extinction of human civilization.

How, then, are We to protect the millions of Our subjects and atone before the spirits of my Imperial ancestors?

This is why We have ordered the Empire to accept the terms of the Joint Declaration. "