How to navigate for free [avoid the hassle of paper maps & expensive roaming charges!]

While preparing our 6-week trip through Japan from South to North via remote areas and major cities, we were a little bit concerned about how to find our way once there: different alphabet, hardly any knowledge of the language, very expensive roaming charges, and various modes of transportation (driving, riding the train, walking and biking in cities, hiking…) seemed tough challenges to overcome to navigate easily. Keep travelling!