Sparked by his meeting with some Bahai followers in 1922, Onisaburo developed an interest in the new language of Esperanto. Esperanto was founded in 1887 by Dr. Ludoviko Zamenhof as a universal language intended to transcend any one nationality or culture.

Onisaburo initiated Esperanto courses at Oomoto in 1923 and wrote a series of 31-syllable poems using a pun in Japanese for each of the 3600 original official Esperanto words, to help in learning the vocabulary.

From 1925 until the Second Oomoto Incident in December 1935, the European Oomoto Center in Paris disseminated information about Oomoto through Esperanto.

During the Cold War, Oomoto used Esperanto as one of the few means of free communication with thinkers and religious people living behind the Iron Curtain.

In recent years, Oomoto has participated in each annual World Esperanto Congress, presenting an Oomoto program concerning traditional arts and joint worship. Oomoto also uses Esperanto for interaction with people in other East Asian countries, sending delegations abroad and welcoming many guests.

In order to support its many Esperanto activities, Oomoto has a full time staff of Esperantists working at the Headquarters. Oomoto´s Esperanto journals are edited by Joel Brozovsky, who has been with the International Department since 1988.

With over 70 years of history in the movemente to establish a universal language, Oomoto´s commitment to Esperanto is a cornerstone of its international activity.