The essence of Ōmine Zenkibō lies in the structure of rebirth: "an oni turning into a tengu." It is a tale that embodies the heart of Shugendō in a single being.

His source lies in the old tales of En no Gyōja and the oni. The oldest extant text depicting En no Ozunu is the Nihon Ryōiki^[2] (early Heian), which portrays him as a thaumaturge who flew through the air commanding demons. The Konjaku Monogatarishū, Book 11^[4] carries the tale of En no Gyōja having demons build a bridge across the mountains, showing the fixing of the image of En no Gyōja as one who commands demons. Zenki was originally a violent oni who carried off human children. En no Gyōja captured him with the secret rite of Fudō Myōō and reformed him into an attendant. By one account, En no Gyōja hid the youngest child of the Zenki couple in an iron cauldron and, through the grief of having one's own child taken, brought them to realize the sin of carrying off the children of others. The reformed Zenki and Goki became dharma-protecting oni and supported En no Gyōja's practice. This Zenki, sublimated into a great tengu at the end of long austerities, is Ōmine Zenkibō. This plot, of a violent being turning into a guardian of the Buddhist law, shows most clearly that the dread of a child-snatching tengu and the faith in a tengu who guards people share a single root.

The Ōmine on which Zenkibō sits is the holy ground of Shugendō. The Ōmine training ground founded by En no Gyōja, and the Ōmine Okugake-michi registered as World Heritage, is a perilous route that ascetics still tread at the risk of their lives, and Zenkibō was conceived as its guardian. He is chanted as "the band of Zenki of Ōmine" in the Muromachi Noh play Kurama Tengu^[1], and stands among the forty-eight tengu of the Tengu-kyō^[3] (some sources give "Nachi Takimoto Zenkibō").

And the heaviest single point of this lore is that the bloodline of Zenki is said to live on into the present. Of the five lodges kept by the five children of Zenki and Goki, only the Onakabō of the Gokijo family remains today, and the present-day Gokijo Yoshiyuki continues to receive the ascetics of the Ōmine Okugake-michi. This genealogy is hard to source explicitly in old documents and is transmitted as the oral lore of the surviving lodge; yet this real continuity—descendants of a reformed oni guarding the path of Shugendō beyond thirteen hundred years—makes Ōmine Zenkibō not a mere legend but a symbol of living faith. Chigiri Kōsai^[5] of tengu scholarship, too, placed him within the system of the great tengu of the many mountains.