Rather than slowing him down, the First Incident jolted Onisaburo into a new understanding of Oomoto´s international role. In October of 1921, he began dictating his great work Reikai Monogatari (Tales from the Spirit World) which eventually grew to 81 volumes.

Sparked by his meeting with a Bahai follower in 1922, Onisaburo became interested in the international language of Esperanto and began making friendships with other religions.

Bankyo Dokon is the title of the 23rd chapter of the Reikai Monogatari, dictated in January 1922. Bankyo Dokon means "All religions spring from the same root". It states the essence of Oomoto´s belief, rooted in the "Oneness" of Nao´s writings, that all religions are expressions of the same divine impulse.

In 1923, the principle of Bankyo Dokon took concrete shape, when Oomoto forged its first affiliation with another faith, the new Chinese Taoist religion known as Tao Yüan. Tao Yüan worshipped five prophets: Lao-tsu, Sakyamuni, Jesus Christ, Mohammed, and Confucius. For Oomoto, the bond with Tao Yüan was just the beginning.