Short answers, pulled from the story.
Major Kenji Hatanaka led the failed coup d'état to prevent the surrender of Japan on the 14th of August 1945. He and his men stormed the Imperial Palace in Tokyo to steal a gramophone record containing the Emperor's surrender broadcast. The coup collapsed because the Emperor's voice was never played to the public.
The Big Six council consisted of Prime Minister Admiral Kantarō Suzuki, Foreign Minister Shigenori Tōgō, Army Minister General Korechika Anami, Navy Minister Admiral Mitsumasa Yonai, and the chiefs of the Army and Navy General Staffs. This group held the fate of the Empire in its hands and was locked in a paralyzing stalemate over whether to continue fighting or surrender. The Army and Navy ministers were hardliners who believed a decisive battle would force a negotiated peace.
The first atomic bomb, code-named Little Boy, detonated over Hiroshima on the 6th of August 1945 at 8:15 am. The Japanese military leadership refused to believe the United States had developed such a weapon and suspected it was a magnesium bomb or liquid-oxygen device. This skepticism persisted even after the second bomb, Fat Man, was dropped on Nagasaki on the 9th of August.
The Soviet Union declared war on Japan on the 8th of August 1945 to invade Manchuria, the puppet state of Manchukuo, and the Kuril Islands. This action fulfilled a promise made to the United States and the United Kingdom at the Tehran and Yalta Conferences to enter the war against Japan within three months of Germany's defeat. The invasion eliminated the last hope of a negotiated peace and opened a new front that threatened to cut off Japan's last source of natural resources.
Emperor Hirohito made a recorded radio address to the Japanese people on the 15th of August 1945, announcing the surrender of the Empire of Japan. This speech, known as the Jewel Voice Broadcast, was the first time the Emperor had ever spoken to the public. The speech was recorded on a gramophone record hidden in a safe by Lord Keeper of the Privy Seal Kōichi Kido.
Foreign Minister Mamoru Shigemitsu and General Yoshijirō Umezu signed the Japanese Instrument of Surrender on the 2nd of September 1945 aboard the battleship Missouri in Tokyo Bay. The ceremony was overseen by the Supreme Commander for the Allied Powers, General Douglas MacArthur. The Allied powers, including the United States, the United Kingdom, China, and the Soviet Union, were represented by their respective commanders.