There was also the risk that Tokyo would be nuked in a decapitation strike if the Japanese leadership did not come to some kind of terms and was being seen as openly unreasonable. I don't know what the fallout of that would be, but having no Emperor and no General Staff or leadership might fuck things up entirely, as without the Emperor's unprecedented speech, as unclear as it was, the surrender of Japanese troops en masse that followed would not have happened. There were of course hold outs anyways, but without that speech, things could have gotten really hairy.
And of course, I wonder who takes command afterwards. Japan might fall apart into warlordism, or someone would step up and agree to peace.