In Japan, except for certain areas in the top major metros, only land has value. Buildings lose value over the life of a 30 year mortgage due to the changing nature of earthquake regulations for buildings. It will almost always be cheaper to tear down and build new than retrofit. Its also why Japan has very creative residential architecture- owners can build what they want without caring about resale.

Many non Japanese who are buying in Japan without understanding this fundamentally different aspect of real estate in Japan do so at their own risk.