There is nothing in Asada's definitive essay regarding your nonsense about the Emperor and a demand for immunity from war crimes, and certainly not as the only necessary concession for a peace agreement.
And that one of the first things that Emperor Showa attempted to do during the occupation was to abdicate. And General MacArthur refused to accept it.
In fact, he offered to abdicate multiple times. The first was right after the occupation started. The second was in 1948 as the War Crimes trials were coming to a close, and he offered to abdicate and even let himself be put on trial, if it would save those facing justice. That also was refused. The final time was in 1951, when the San Francisco Peace Treaty was close to being signed and the occupation ended. He again tried to abdicate, stating he would renounce the throne and all titles and take up life as a civilian. That way his son could take the throne without any influence from his reign.
That also was rejected.
So if it was so damned important that the Emperor not be removed or tried, why did he offer that himself later?
What people tend to not grasp is that the person of the Emperor is not even important, just that there is an
Emperor of the Imperial Line on the throne.
"The King is dead, long live the King."
This is a concept that far to many seem completely unable to grasp. The closest we have in modern days is probably the Pope. Which Cardinal throws off their red robes and sits their butt in the Chair of Saint Peter really does not matter, so long as the butt of some high ranking Catholic occupies it. The Catholic population also largely could not care less, so long as it is a Catholic butt. In Japan, it is much the same. So long as one of the Imperial Line has their butt on the Chrysanthemum Throne.
This is why once again we have seen a return of "Cadet Houses" into the line. I already discussed their being removed in 1947, but so far there has been one cadet line restored.
And for those that do not understand and are to lazy to look up what that means, let me explain. A "Cadet House" is when a member of the royal line branches off. They are no longer in line of secession, but are still of the Imperial Blood Line. And under Japanese law and traditions, their children could ascend to the throne if no others were alive or able. After Emperor Emeritus Akihito's younger brother Prince Yoshi got married, their father created the first (and only) cadet house and elevated him to Prince Hitachi. But he had no children, so that cadet house will die with him.
It is hoped that the 2nd in line Prince Akishino is fruitful, because the entire 2,500 year old dynasty still rests on his head (or other parts). The hope is that in another decade or so he has many sons, so they can repopulate the cadet houses and not be reliant upon a single line to keep the lineage alive.