Japan’s population is shrinking. Less babies are being born.
Japan’s (mostly) one race culture is not allowing much foreign immigration to supplement the retired workers. The retirees are soaking the medical system mightily.
Japan, just like Italy, may be close to dropping down in influence due to the reduction of native born who desire to promote and continue the traditional lifestyles of generations past. Do not forget Portugal used to be one of the main epicenters of world trade and monetary power. That country still exists on the map, but mostly as an afterthought for tourists.
And their soccer players.