There are way more complexities than meet the eye here.
Not the least of which: just buying property doesn't give you a way to extend a visa beyond the normal tourist period (usually 90 days per 6-month period). Japan ultimately is still an isolationist country, and it shows the most in its immigration policies.
But they're japanese, so the most they can do is knock insistently on the door; something like kicking the door down would be rude. And if you marry, you solve the visa problem and help repopulate. Two birds one stone.
Jokes aside, the place is really rundown and also not much "classic/picturesque", looks more like an old factory or warehouse.
Oh, I get that. I guess I'm suggesting there are better options if it's hiding out without an appropriate visa in the woods. It's probably easier in, say, Borneo.
The Japanese government functions and has enforcement of immigration policy.
Correct. There is no "I own property" special visa status. The 90 day/6 mos can even be denied for any or no reason by immigration if they think you're shady meaning zero access to the property.