Last year, the government passed a law covering minpaku, which is when people rent out space on their properties to travelers (a la Airbnb). The law is part of an effort to regulate accommodations amid a tourism boom ahead of the 2020 Olympics.
One issue for non-Japanese travelers, though, has been whether they must show ID such as a passports at check-in.
For hotels, which fall under the Hotel Business Law, the regulation has always been this: For any adult, Japanese or non-Japanese, who has an address in Japan, ID is not required. You just write your contact details in the guest registry. However, for guests who don't reside in this country, displaying ID (i.e., your passport) is required.