I am finding more and more interesting stuff on the old Time archives as I thumb (figuratively) through them. The Japanese news agency Domei announced this when the Emperor accepted the terms of the allies. It was also reported in the Time magazine of late August, 1945: Domei described the scene at which Emperor Hirohito decided to surrender to the Allies: "On the personal initiative of His Majesty, an historical conference was held before the Throne at the Imperial Palace. . . . The conference was attended by Premier Baron Kantaro Suzuki and all other ministers. . . . "After all stated their opinion, His Majesty was graciously pleased to make the final decision, stating that . . . whatever the future may bring in regard to his personal safety he should not like to see any more of his subjects killed and the country reduced to scorched earth. . . ." Thereupon Hirohito broke down, sobbed, wiped his tears away with his white-gloved hand. His ministers and aides, "profoundly impressed by the gracious concern of His Majesty . . . silently bowed down and wept. Thus the final decision to accept the terms of the Potsdam declaration was taken." See: JAPAN: Tears - TIME
Japan's Longest Day covers this in detail. (I hope I got the title right, I'm juggling Mills bombs without pins right now.)