Tokko-no-yu is the historic birthplace of Shuzenji Onsen and the oldest hot spring in the Izu Peninsula. Legend says that the Buddhist monk Kobo Daishi created it in 807 AD by striking a river rock with his ritual wand (tokko) to provide warm water for a devoted son. Located in the center of the Katsura River, this open-air stone basin is the town's iconic symbol. Today, it is preserved for viewing only; soaking or foot bathing is not allowed.