this video intrigued me so I looked it up and found this interesting review of the film on vulture:

Minus One has no other kaiju but Godzilla, and it takes the monster back to his roots — before that, actually. Whereas the original 1954 Godzilla, a thrilling metaphor for the atomic bomb released just nine years after the end of World War II, takes place in the year it came out, Minus One is set in the immediate aftermath of the war, an era when a demilitarized Japan’s government was in shambles, the cities largely firebombed (or worse) to hell, and its people left searching for new meaning after the disastrous outcome of a war the imperial government started with such ambitious hopes. Japan was at “zero,” and the arrival of Godzilla sets it back to “minus one,” hence the title.