The Three Demon Gods and Their Original Buddhist Forms. Sanki Daigongen consists of three demon gods: Tsuicho Kishin, Jibi Kishin, and Mara Kishin^[1]. Tsuicho Kishin governs good fortune and has Dainichi Nyorai as its honji-butsu; Jibi Kishin governs wisdom and has Kokuzo Bosatsu as its honji-butsu; Mara Kishin governs the subjugation of evil and has Fudo Myoo as its honji-butsu. Oni are originally beings that evoke fear in humans, but here they are transformed into benevolent deities that ward off demons and protect sentient beings. The assignment of the three virtues of fortune, wisdom, and subjugation to the demon gods reflects a unique form of faith born from the fusion of mountain Buddhism and tengu worship.

Invitation by Kukai and the Founding of Mount Misen. It is said that Kobo Daishi (Kukai) founded Mount Misen in the first year of Daido (806), and the enshrinement of Sanki Daigongen at that time is considered the origin of its worship^[2]. Near the summit of Mount Misen is the Reikado (Hall of the Spiritual Flame), which houses the "Kiezu-no-Reika" (Unextinguishable Spiritual Fire), a goma fire lit by Kukai during his ascetic training that is said to have been burning continuously day and night for 1200 years. This fire also served as the source for the "Flame of Peace" in the Hiroshima Peace Memorial Park. Sanki Daigongen was originally enshrined at Oyama Shrine, the main shrine of Mount Misen, but was moved to the current Sankido following the Shinto and Buddhism Separation Order in the Meiji era.

Masanori Fukushima's Tengu Extermination Legend. During the Edo period, it was said that tengu appeared on Mount Misen. Masanori Fukushima, the daimyo of Aki Province, went to Mount Misen to exterminate the tengu, but was terrified by their majesty and fled. Later, he built the magnificent Sankido and worshiped devoutly, after which the tengu are said to have never appeared again. The belief that Sanki Daigongen commands large and small tengu as familiars is closely linked to the folk tradition that Mount Misen is a sacred mountain inhabited by tengu.

Hirobumi Ito's Veneration and Modern Faith. The first Prime Minister, Hirobumi Ito, is said to have deeply believed in Sanki Daigongen and contributed to the maintenance of the pilgrimage paths to Mount Misen. Today, Sankido continues to attract worshippers seeking safety for their families, prosperity in business, and protection from disasters, forming the core of faith for pilgrims visiting Miyajima and Mount Misen, alongside Itsukushima Shrine and Daisho-in Temple. Due to the rare nature of worshiping oni, it is widely known as "Japan's only oni deity."