According to tradition, when Saicho, the founder of the Nihon Tendai sect, founded Tokko-ji Temple in 805 after arriving at the area following his studies in Tang (China), he endowed ancestors of the Yokooji family, who cooperated in the founding of the temple, with 法火 (hori no hi flame) and Bishamon-ten-zo (statue of Bishamon-ten (Vaisravana)) as a token of gratitude.
伝承によれば、805年（延暦24年）、日本天台宗の開祖である最澄が唐での留学を終え、当地に上陸し、独鈷寺（新宮町立花口）を開基した際、協力した横大路家の先祖にお礼として法火（法理の火）と毘沙門天像を授けたという。