Most japanese GPS will take landline numbers as that's more reliable (and much, much easier to input) than addresses. The alternative is a proprietary location system (Denso's MAPCODE).
It doesn't help that a lot of streets in Japan don't have names.
I have a friend living in a small town in Japan that can't get mail at his apartment because the building doesn't have an address. He has his mail delivered to the closest building that does have an address, and they give it to him.
> It doesn't help that a lot of streets in Japan don't have names.
That's because Japan doesn't generally use street-based addressing, it's area-based from top to bottom, so street names are replaced by block numbers (I guess small villages could be blockless and jump directly from village to building as well).
I have a friend living in a small town in Japan that can't get mail at his apartment because the building doesn't have an address. He has his mail delivered to the closest building that does have an address, and they give it to him.