Because other locations are not experiencing a surge, Japan is. Which means a strain may be circulating there and not in other locations. Would be interesting to find out what is the dominant strain of Covid in this situation.That's not necessarily the case now. Why would the unvaccinated in Japan require hospitalization and have deaths at high percapita rate as other locations? Keep in mind that more people are vaccinated there, and have had more rounds of boosters. It's difficult to figure out since the reasoning behind vaccination would point in the opposite direction.
I hope it's not evolving like the flu, where last years' flu shot is ineffective against this years' new strains.