Morihei Ueshiba and his art, Aikido, was said to be a product of his martial and his religious tradition. Even students who are ignorant of the Daito Ryu tradition but know Aikido will watch a Daito Ryu demo and see something they recognize. They might see a new (to them) variation, or might decide they want no part of the ukemi, but it will be familiar. Morihei Ueshiba was officially teaching Daito-ryu until the late 1930s.
Aikido is often called a synthesis of Ueshiba's martial training and his religious beliefs. The Oomoto Kyo faith is acknowledged as his chosen religion. Onisaburo Deguchi is the man who Morihei Ueshiba met when he was returning home to see his sick father. Ueshiba arrived to ask for prayers for his father's good health, and instead remained with Deguchi for several days before resuming his trip home - arriving too late to say goodbye. Ueshiba then left Hokkaido, leaving both the settlement he had helped found and his Daito Ryu teacher, to move to Ayabe in 1919 to join the Shinto sect. He opened his first dojo on Oomoto Kyo grounds.
The First Oomoto Incident would happen in 1921 when the government intervened and denounced the Oomoto Kyo faith. The promotion of the Imperial Way and the divinity of the Emperor as the descendant of Amaterasu was being challenged by Oomoto Kyo's support of other deities. In supporting Onisaburo and Oomoto Kyo at this time, Ueshiba risked being arrested along with Onisaburo as several other Oomoto Kyo leaders were. Released on bail, Onisaburo began dictating Reikai Monogatari, The Tale of the Spirit World. Ueshiba would have been present for the writing.
Ueshiba had two sons die of illness on the Oomoto Kyo property, and he left his third, the eventual Second Doshu Kisshomaru, behind when Deguchi chose to violate the terms of his probation following the First Oomoto Kyo incident. Risking arrest, imprisionment, and death, Morihei travelled with Deguchi to Mongolia in 1924, apparently in an attempt to set up Onisaburo Deguchi as the next Dalai Lama or reincarnation of Genghis Khan (sources seem to differ, but this was to be a religious utopia, with Deguchi as the leader.) The attempt failed. The Chinese men who allied themselves with Deguchi and Ueshiba were killed by firing squad and the Japanese Consul took Onisaburo Deguchi and Morihei Ueshiba into custody. Ueshiba would avoid arrest during the Second Oomoto Incident in 1935 that left Deguchi imprisoned for several years.
I have some recognition of the Daito Ryu roots in my Aikido. When I read up on the substance and source of Ueshiba's spiritual beliefs; when I read up on Deguchi and Oomoto Kyo beliefs - I recognize far less of the Oomoto Kyo roots in my Aikido.
Esperanto is a constructed language created by a Danish Opthamologist that was an attempt at an international language; the language is endorsed by the Oomoto Kyo religion and the language's creator is now deified. Per Wikipedia, the religion has published books and magazines in Esperanto since 1924 until the present day. Almost all active members of Oomoto Kyo have apparently studied some Esperanto.
A central belief of Oomoto used to be spirit possession - the whole sect was started by a peasant woman, Deguchi Nao, who became the vessel for a spirit that left many automatic writings. Onisaburo, who had a variety of spiritual techniques already, married her one daughter and became a leader in the sect. Onisaburo Deguchi banned induced spirit possession, Chikon Kishin, in 1923. Ueshiba would have been living with Deguchi for approximately four years during the time this practice was apparently most widely practiced. Onisaburo apparently made the induced spirit possession illegal just before he and Ueshiba would leave for Mongolia.
The whole theory of technical evolution, Aikido evolving away from Daito Ryu, is based on Oomoto Kyo and Onisaburo Deguchi's spiritual influence in the stories. Not only is there little supporting the O Sensei evolution, but what is Deguchi's influence on Aikido? This spiritual mentor who guided Ueshiba towards enlightenment- what part of my Aikido can I point to as Deguchi's influence?
Deguchi apparently had a huge influence on Ueshiba himself. When the story of Ueshiba breaking ties with Takeda is told, it is usually Ueshiba's enlightenments and his spiritual practices that are the motivation. I have been lead to believe Aikido is physically and technically different from Daito Ryu because of Ueshiba's spiritual practice. I have not been able to clearly say what this spiritual belief or practice was, so I've been looking into it lately. I have no concrete conclusions; I'm just enjoying the ride.
Christopher Li offered these two sources as translated examples of Deguchi's writings. The Sangenkai website is an amazing, serious resource that I recommend to anyone. There are materials available there that do not exist anywhere else.