Everyone knew that the survival/position of the Emperor was in fact a condition - but, as the only condition, it left him as a figurehead only - and figureheads can be very useful. Think, King Herod under the Romans.The emperor should have been arrested, imprisoned, tried, convicted and hung in Tokyo for all to see.
. . . which would either have required the US to break its word after the fact, or would - again - have meant the continuation of hostilities. We know that the Japanese military almost prevented the surrender even with the condition of the retention of the Emperor.The point about Unconditional Surrender was the bitter reflection on what the US military - Pershing, I believe - said about the armistice that ended WWI. Namely, that the trouble with stopping the fighting at that point was that although the Germans were defeated, they did not know it and admit it. And that is why WWII came on two decades later, actually as an extension of WWI.The difference at the end of WWII in Japan was that although they had retained their emperor as a figurehead useful to the US, and could cling to some modicum of self-respect on that account,the Japanese were under US occupation and they knew beyond peradventure that they had been beaten. So, as history shows, nothing close to a reprise of WWII was attempted by Japan. Not twenty years later, and no sign of it seventy years later. Killing the emperor might have been shadenfreude - but it would have been too expensive to attain, and also too expensive in its effects.
We all have our opinions. A lie is a lie is a lie. A rose by any other name is still a rose.