The Onsen is said to be newly discovered in the 5th century when Emperor Seinei went to visit Kumano. Legend says that two elderlies who came from Ise had paid respect to the locals for their kindness and stroked the ground with a branch of a Sakaki tree causing hot water to gush out. Later, Kobo Daishi built a Yakushido to express his gratitude towards the medical efficacy of the spa and named it Rurikouzan Tousenji Temple.