Nevertheless, if housing is so affordable in Japan, why are there still people who don't own homes? Can an average McDonalds worker in their 20-ies just go and buy a home easily without applying for a lifetime-long mortgage?
You literally have it the wrong way around. There's less incentive to own homes in countries where housing prices fall. Owning a home actually costs you money, it isn't a good investment in the absence of artificial scarcity. In Japan a house is a consumer good like a car, in fact on average the value of most houses drops to about zero in 30-40 years.
Some of the richest countries in the world have the lowest rates of personal home ownership, Switzerland, Germany, Japan among them because it isn't an investment vehicle and rent protections are good. This narrative of being desperate to own a home just doesn't make any sense.
Mostly because they don't need or want their own house and/or they spend their money on other stuff.
> Can an average McDonalds worker in their 20-ies just go and buy a home easily
The median McDonalds worker in Japan is 17 and lives with their parents. And maybe 3/4 of the ones who aren't teens are freeters.
If you don't make a lot of money you can certainly buy something but it won't be the nicest or in the best location.
> without applying for a lifetime-long mortgage?
Many people buy with cash, many get nicer homes with 35-year mortgages at super low interest rates.