The Shimanto is called Japan's last truly clear river, and the description is precise: no large dams interrupt its flow for most of its length, and the water runs at a clarity that feels anachronistic. Canoeing it — past the low-water bridges called chinka-bashi that disappear beneath the surface during floods — is a way of understanding what Japanese rivers used to be like, and still are, here. The experience is simple in structure: a paddle, a canoe, a stretch of river, and several hours in which the main decisions concern where to stop for lunch and how hard to work against the current. The complexity is in what the river provides in exchange. The sound changes when you are on the water rather than beside it. The bridges look different from below. The mountains on both sides are simply there, not framed or managed. The Shimanto valley is not easy to reach from anywhere. This is part of what has preserved it. The canoe operators who run tours on the river tend to be people who chose to live here, which means the experience of booking a half-day trip often includes a conversation about why someone would want to.