You know, I don't want to play down your legitimate concerns, but --

Japan is a first world country. They have these things called cabs. Unless you are really headed out into the inaka to some mountaintop temple or somethng, you will be able to just have a cab deliver you right to the front door of virtually anyplace you are likely to stay.

The only place I have ever had a problem with a rolling bag is in some of the larger cities where they don't have crosswalks but rather pedestrian overpasses, some of which don't have elevators. Hauling the bag up those stairs can be a chore. In the very few cases where I did that, if I had it to do again, I would probably take a cab the 2 blocks just to avoid the hassle.