Haruna-ko Ryujin Legend

The Haruna-ko ryujin legend is a mountain-cult cycle in Kozuke Province (Gunma), centred on the dragon deity in Lake Haruna, the summit crater lake of Mount Haruna. The lake-master is described as a paired male-and-female dragon-serpent, worshipped together with Homusubi-no-Kami and Haniyama-hime-no-Kami at Haruna Jinja on the lower slopes. The lake dragon, as master of rain and water, holds the twofold benefit of protecting agriculture and preventing fire. From the medieval period, in the Shugendo framework, Haruna joined Akagi and Myogi as the three mountains of Kozuke and was understood as the deity governing the water source and weather of the Kanto plain. The structure has three parts: appearance of the lake dragons (male and female); rain-prayer rite at Lake Haruna and village ritual; and the establishment of mountain worship at Haruna Jinja. The pairing of lake and dragon is also seen in the Akagi Onuma tradition and the omiwatari ice-crack at Lake Suwa, sharing a structure of volcanic-crater-lake worship. The mountain-and-water-deity layering is distinctive. The site is Lake Haruna in Haruna-ko-machi, Takasaki (Gunma), with Haruna Jinja midway up the mountain in Haruna-san-machi. The shrine's main hall, set against rock walls, is a representative iwakura form of Shugendo. With Akagi (Maebashi) and Myogi (Tomioka), Haruna forms the three mountains of Kozuke, the core of Kanto mountain worship, and was widely prayed to against drought. Sources include the medieval Haruna-san Engi, the Edo gazetteers Joshu-koku-shi and Jomo Densetsu Zakki, and the Engishiki Jinmyocho, which records a predecessor of Haruna Jinja. Rain-prayer practice is treated in Yanagita Kunio's study Amagoi Shuzoku no Kenkyu and in the folklore volume of the Gunma prefectural history. The cycle is an independent regional tradition outside the Kiki corpus.