This is not a new discovery that it was officially announced that Gen. Lemay was given Grand Cordon of the Order of the Rising Sun on December 7, 1964 by the Japanese government for his great contribution to training the Japan Air Self-Defense Force.
What it meant was that there would be no chance in the future that Japan would regard him as a war criminal.
He only did what he had to do as a military man and the war was over.
Japanese public at the time did not necessarily accept that as it was but it was a realistic political decision to go forward in the history.
Here is a NHK video in 1978 introducing retired Gen. Lemay and his Medal at 9:04
View: https://www.youtube.com/watch?v=ThvwC3XkgCo