I mostly used Frank's Downfall for the quotes in Surrender of Japanit's the best single reference I know.
 The emperor made his decision on the night of August 9–10: "...Nevertheless, the time has come to bear the unbearable.... I swallow my tears and give my sanction to the proposal to accept the Allied proclamation on the basis outlined by the Foreign Minister." That being the one-condition position, which the cabinet then accepted. But the Allies didn't, so there followed a couple of days of telegrams back and forth. The surrender wasn't a done deal until August 14, when the Japanese gave up on an explicit guarantee for the Emperor: "I have listened carefully to each of the arguments presented in opposition to the view that Japan should accept the Allied reply as it stands and without further clarification or modification, but my own thoughts have not undergone any change."
 I linked to it before, but here's an interesting first-hand account: