Motoyu Hakoyama Onsen sits nestled on Hakoyama in Yamanouchi Town. It is a day-use onsen and minshuku known for its free-flowing hot spring that changes color between green and brown depending on the day, and for a Showa-era retro diner. The bathing area includes a Finnish sauna with a mild heat that lets you take your time working up a sweat. The cold plunge bath immediately adjacent to the sauna is continuously fed with well water and, because there is no chiller, can become extremely cold, reaching single digits (below 10°C) in winter. Sitting on the rock-lined open-air bath and feeling the natural breeze during outdoor cooling is a special experience.