This video about Tsuetate Onsen (in the Oguni area, north of Aso) is in Japanese but the YouTube page includes the following English explanation:
“Located in Oguni-machi Aso, the Tsuetate-Onsen Hot Springs have a 1800-year history. Thanks to its exquisite spring quality, the area has flourished as a Hot-Spring resort since old times. In recent years, it is winning popularity with modern twists on nostalgia- such as a retro back-alley tour guided by the local people, a revived regional sweets (puddings), and NEO TOJI, a new style hot spring therapy.”
