I had spent considerable time just planning on what luggage we would take. When you go to Japan, you must count on a great deal of walking just to get from hotel to hotel. Huge, crowded airports and train stations, up stairs, down stairs, tight schedules that give you only minutes to embark or debark. And you will have to carry your luggage for most of that time.
My advice is to never, never take more than you can carry yourself in one trip. As such, I still ended up with three bags. A rolling cart backpack for clothing with a small removable day pack, a backpack computer bag for my electronics and finally, pictured here, a small shoulder bag for my camera gear. In an extreme worst case, I could carry everything on my back and shoulders for a fair distance or stack everything on the rolling backpack for longer distances.