The effects of the "Twin Shocks"—the Soviet entry and the atomic bombing—were profound. On 10 August the "sacred decision" was made by Japanese Cabinet to accept the Potsdam terms on one condition: the "prerogative of His Majesty as a Sovereign Ruler". At noon on 15 August, after the American government's intentionally ambiguous reply, stating that the "authority" of the emperor "shall be subject to the Supreme Commander of the Allied Powers", the Emperor broadcast to the nation and to the world at large the rescript of surrender, ending the Second World War.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): What was the one condition Japan wanted before accepting the Potsdam terms?
"prerogative of His Majesty as a Sovereign Ruler"