Most of Honshu is mountainous and they planned to keep fighting there. Huge underground bunkers were being dug near Nagano for the government and royal family. It was a closely guarded secret during the Nagano Winter Games because the Japanese didn't want any reporters snooping around and writing about the WWII plans for Nagano.
There were still dozens of caves when I was there in the 1950s as an Army Brat.
A few Japanese families lived in the caves in Yokohama not far from our house.
A couple of caves had openings in the Army’s Area 2 Dependent’s Housing Area in Honmoku and an American kid got hurt in one of them and had to be rescued.
The MPs ordered that all the caves be filled with cement to put a stop to potential accidents in ‘59 or ‘60.