To be brief, I booked accommodation in Japan with Airbnb between March and July for a couple of places in Japan, different cities I was going to travel to. Japan's government changed the law on 1st of June and said all hosts must be licensed in order to have guests over and certain local governments went further to say you can only be a host a certain number of days per year.
Airbnb obviously want to have a market in Japan, a country of 127 million people ( source = google "japan population")
and approx 28 million overseas residents visits to Japan per year (https://www.tourism.jp/en/tourism-database/stats/inbound/#annual), so Airbnb comply with the law. This spells trouble for holiday makers who don't know if the host is registered or not. For me I contacted Airbnb support and they said that I'd get a refund and a voucher from Airbnb if a host was forced to cancel.
2 hosts cancelled on me ( 1 on my profile and 1 on my girlfriend's Airbnb, she booked some of the accommodation for me) and I got a refund back to my bank account, a voucher for a trip worth the amount of the trip and 100$ to spend on an Airbnb experience. Airbnb in this situation went above and beyond and if someone had to book accommodation above the cost of what they originally booked, Airbnb would have refunded the difference to them from a fund they set up ( within reason, if someone booked 5 star everything when 3 star was available, they might not I'm not sure). We used the Airbnb experience to learn how to make udon noodles in Osaka, which was nice.
Over time hosts will get registered with the government in order to remain listed on Airbnb, but the bottle neck was that the government couldn't process all the applications on time for bookings already made on the site. In my opinion government regulation is expected at some point but the way the government forced Airbnb to cancel so many reservations on short notice was atrocious. If a host didn't have a license within 10 days of the start of the hosting period,through no fault of their own, even though they applied for one, the booking was cancelled. Many hosts will have lost out on income during the busiest part of the year which is a shame for people trying to support themselves and their families. Some hosts may have organised directly with the guest to still allow them to stay off Airbnb, which hopefully helped the host and guests out.
Overall regulation might have some good aspects for the host and the tourist but I expect it is just another unnecessary cost of time and information. For the host I stayed with who was registered, I had to submit passport photos and other information to them, which I was uncomfortable with.