The park is named after Tokko-no-yu, the oldest hot spring in the Izu Peninsula. According to legend, in 807 AD, the famous Buddhist monk Kobo Daishi (Kukai) visited the area and saw a boy washing his sick father in the cold waters of the Katsura River. Touched by the boy's devotion, the monk struck a river rock with his tokko (a Buddhist ritual implement), causing hot spring water to gush out and miraculously heal the father. Today, the park serves as a monument to this birth of Shuzenji's onsen culture.