The Shimanto is Japan's longest undammed river and its clearest — called "the last clear stream in Japan." The 196km river flows through remote Kochi Prefecture, crossed by 47 chinkabashi (submerged bridges) with no railings, built to flood and survive rather than resist. The riverside road traces the river from its lower reaches upstream through quiet farming hamlets and cedar forest.
Clone it to your planner, customize dates and stops, then ride. All free.