My understanding was that Japanese housing costs are only good in USD because the yen is devalued. I had the impression that housing is expensive relative to local wages. Is that not true?
It's not true. Here is an apples-to-apples comparison of the price of residential property between the US and Japan in real (inflation adjusted) terms.
https://fred.stlouisfed.org/series/QJPR368BIS
https://fred.stlouisfed.org/series/QUSR628BIS