I won't do your research for you, but various factions within the Japanese leadership wanted to put lots of significant things on the table, like maintaining the seat of the emperor, the existing political structure, etc. All were showstoppers to the US.
But that isn't true. The seat of the emperor was maintained, at least nominally, so it clearly wasn't a showstopper. The US may have demanded unconditional surrender before the atomic bombings, but it accepted a conditional surrender after.
1945: Japan signs unconditional surrender > Japanese officials have signed the act of unconditional surrender, finally bringing to an end six years of world war.
> Under the terms of the ceasefire, Japan has agreed to end all hostilities, release all prisoners of war, and comply with the terms of the Potsdam declaration, which confines its sovereignty to the four main islands which make up Japan.
> Under the terms of the ceasefire, Japan has agreed to end all hostilities, release all prisoners of war, and comply with the terms of the Potsdam declaration, which confines its sovereignty to the four main islands which make up Japan.
> It has also agreed to acknowledge the authority of the US supreme commander. Although Emperor Hirohito will be allowed to remain as a symbolic head of state.
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I'm pretty sure the surrender was unconditional and later the Allies announced that the Emperor would keep his position(probably mostly to help ease the occupation) ---
> www.history.com/this-day-in-history/japan-accepts-potsdam-terms-agrees-to-unconditional-surrender
At the behest of two Cabinet members, the emperor summoned and presided over a special meeting of the Council and implored them to consider accepting the terms of the Potsdam Conference, which meant unconditional surrender. "It seems obvious that the nation is no longer able to wage war, and its ability to defend its own shores is doubtful." The Council had been split over the surrender terms; half the members wanted assurances that the emperor would maintain his hereditary and traditional role in a postwar Japan before surrender could be considered. But in light of the bombing of Hiroshima on August 6, Nagasaki on August 9, and the Soviet invasion of Manchuria, as well as the emperor's own request that the Council "bear the unbearable," it was agreed: Japan would surrender.
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> www.history.com/this-day-in-history/japan-accepts-potsdam-terms-agrees-to-unconditional-surrender
From Wikipedia[1]: 'Japan's ambassador to Switzerland, observed that "unconditional surrender" applied only to the military and not to the government or the people, and he pleaded that it should be understood that the careful language of Potsdam appeared "to have occasioned a great deal of thought" on the part of the signatory governments—"they seem to have taken pains to save face for us on various points."'
So it seems that both Japan and the Allies understood that unconditional surrender only applied to Japan's military.
Further: 'That day, Hirohito informed the imperial family of his decision to surrender. One of his uncles, Prince Asaka, then asked whether the war would be continued if the kokutai (national polity) could not be preserved. The emperor simply replied "of course."'
In other words, Japan was willing to continue fighting, even after the atomic bombings, if it didn't get to insist on a few conditions. That doesn't sound like unconditional surrender to me.
I should also point out that the parent of my original post asserted that any and all Japanese conditions were "showstoppers." I pointed out that, whether or not the emperor's seat was a condition explicitly writing into the surrender documents, at least one of Japan's surrender conditions, namely keeping the emperor in place, was clearly not a showstopper.
"Unconditional" doesn't mean "there are no terms." It means that the loser dictates no terms, while the victor dictates all the terms.