Emphasis on Tokyo, which was basically the only place in Japan that's still growing, until it too started shrinking during COVID.
Go to any second-tier city, or even much of suburban Tokyo, and you'll see urban collapse in action: emptied-out "shutter-gai" shopping arcades, closed restaurants and hotels. Then drive out into the countryside, and you'll see completely depopulated hamlets and virtually all businesses not catering directly to agriculture have already collapsed.