Someone with more knowledge than me could probably explain this better though.
Local municipalities are going to be very skeptical of anyone without residence buying such a home.
https://en.wikipedia.org/wiki/List_of_castles_and_fortresses...
https://www.thelocal.ch/20220104/gambarogno-the-latest-swiss...
It floundered, because it wasn't just practical to do anything in such a remote place.
I know someone who tried to pull that stunt and bought a house in Detroit for just a few thousand dollars. It really did not take the city all that long (less than a year for sure) to decide he was not going to fix the place up. They made him an offer he could not refuse -- give it to the Detroit Land Bank for nothin, or go to court.
Of course that drastically over-simplifies the realities of moving to Japan and won't work for everyone but just a thought process I go through every so often.