I'm sure the majority of Japanese would welcome American military help should the North Koreans or Chinese arrive uninvited on their shores. It's just that no one wants a U.S. base in their backyard.
I thought I'd heard all the arguments ad nauseam night after night on NHK news. There's the issue of safety of course and crime. But for some unknown reason no mention is ever made of the fact that SDF aircraft have been known to fall out of the sky and that far more crimes are committed by Japanese than American military personnel.
But the clincher was when the people of Kagoshima said they wouldn't accept any of the Futenma Air Station's operations because the proposed site is where they hold bullfighting.
Now in terms of the security of a nation and its people, that's ridiculous.