En no Ozuno, recognized as a mystic and an apothecary, condemned to the island of Izu Ōshima, was a prominent figure in the early cultural landscape of Japan. Straddling the lines of religion, culture, and medicine, Ozuno was known for his alternative healing methods and spiritual practices, which intertwined Shinto and Buddhist beliefs. His banishment in the late 7th century resulted not only from the growing unease among authorities regarding his unconventional practices but also signified a broader apprehension about the emergence of new religious movements in a period of significant cultural transformation in Japan.

Izu Ōshima, an island in the Izu Archipelago, became a sanctuary for Ozuno during his banishment. The isolation allowed him to deepen his spiritual practices, and it was during this period that his teachings began to crystallize into what would later become Shugendō—a folk religion emphasizing ascetic practices, mountain worship, and the pursuit of enlightenment. This religion would eventually gain a substantial following, appealing to those who sought a connection with nature and the spiritual world.

Ozuno's time on Izu Ōshima was not simply a period of exile; it was a transformative phase that allowed him to gather his thoughts and refine his beliefs. The natural beauty and spiritual essence of the island profoundly influenced his ideas, leading him to articulate a vision that would resonate with future generations. Upon his return, his teachings attracted followers, leading to the formation of a new spiritual community centered around his practices and philosophies.