So Japan is slowly but surely testing the waters as it reopens the border. Today, June 7th, the new rules were announced. To put it simply, there are now three country categories: Red, Yellow, and Blue. The rules for entry differ depending on which group your country is in, but for blue (which covers most of Europe and North America), there is no quarantine on arrival in Japan, and you do not have to be vaccinated. But, you do still need a valid PCR test done 72 hours before entry to be eligible. The border has now opened to tourism, but only for tour groups run by certified travel agencies. All entrants have to apply for a visa.
I imagine that they will run with these rules till at least the end of summer, and at that point will look toward allowing individual tourists to enter the country again. It's been a wild 2 years!