Been trying out diff apps out.  I just came back from Japan which they don't sell non residents sims. 

Mapswithme which I bought for a few bucks allows me to save points.  Or import points off Google Earth as well.  Can download entire country maps. 

OTOH there is Orux which you can download other maps as well like sat images but each is limited to 512MB which doesn't cover Tokyo CBD but the sat images are more detailed not so much the small buildings but large buildings and landmarks and knowing on the screen if it is a main road an alleyway is handy. 

I know that some people use Orux b/c they can get sat images but I am wondering if the bother is worth it.  One would need to save many diff maps if they are doing more than just seeing (1) CBD.