Erick - last try.
1. This "all experts" site is exactly what I'm talking about - uneducated people who regurgitate stuff they glean from other English language publications, particularly those about aikido. There is NO record of Nakai studying Yagyu Shinkage-ryu.
None. Furthermore, Ueshiba's training in Shingan-ryu was quite cursory. He mostly learned the jujutsu portion, to some degree - and NOT the weaponry, which is over half the school. And the jujutsu he learned left him absolutely inept when he faced Takeda Sokaku for the first time.
2. And now you include yourself among those "uneducated" - I am not making an ad hominem attack - I'm stating this as a fact. You logged onto the Yagyu Shingan-ryu site (Arakido) and inferred something that is not true. Otsubo Shiho never trained a day of Yagyu Shingan-ryu in his life. Muto Masao, separately studied Yagyu Shingan-ryu from another teacher and then went to study Shinkage-ryu with Otsubo. People at the time commented on this as being quite unusual - I remember it at the time. I heard several noted koryu people say something like, "Hmm, Mutoh-san might be biting off more than he can handle. Shingan-ryu and Shinkage-ryu are so different!" Yet you assert from your misreading of the website that Otsubo did Shingan-ryu.
3. That Ueshiba used the word "love" in his last years has no particular relevance to Yagyu Shinkage-ryu and Ueshiba.
From Ueshiba… at that time I was about 40 years old. One day I was drying myself off by the well. Suddenly, a cascade of blinding golden flashes came down from the sky enveloping my body. Then immediately my body became larger and larger, attaining the size of the entire Universe. While overwhelmed by this experience I suddenly realized that one should not think of trying to win. The form of budo must be love. One should live in love. This is aikido and this is the old form of the posture in kenjutsu. After this realization I was overjoyed and could not hold back the tears.
That was an interview at the end of his life. Ueshiba, in the 1920's called what he did, Daito-ryu. He revinvented his "enlightenment" story over and over again. What he as an old man, propounding his own mythology wrote, is not evidence of any training that might have occurred in the 1920's or earlier.
BTW - Mutoh Masao rather gleefully told me that he had a copy of Admiral Takeshita's diary and - here's a direct quote, "Everyone today talks about 'aikido is love, love, love.' But Takeshita sensei quoted Ueshiba-san as saying, "Aiki is a means of achieving harmony with another person so that you can make them do what you want."
4. Otsubo would have seen Ueshiba in the 1950's or 1960's, not the 1920's. I knew Otsubo, and had conversations with him in the 1980's. He was a little boy in the 1920's - and not yet trained in Shinkage-ryu. So this, too, has no relevance.
In sum, your supposition is based on a number of incorrect assumptions. A) that contrary to record, Ueshiba might have studied Shinkage-ryu from a man who never knew it (Nakai). B) Or, that he learned about the "love" of YSR from Takeda Sokaku (now there's a thought!) C) that Otsubo knew Yagyu Shingan-ryu
D) That Otsubo must have seen Ueshiba before he cross-trained with Gejo (in a time machine?). e) that his mythologizing self-references in the 1960's, using the term "love," something he used only after the war, I believe, is in any way proof of an initiation into Yagyu Shinkage-ryu.
Final point, Ueshiba did NOT study with Gejo, who was his
student. Ueshiba had him show him some forms which, as was his wont, he altered to fit his aiki-agenda (these forms, no longer Yagyu Shinkage-ryu in anything else but outer structure, were taught to Hikitzuchi Morio). His training in YSR, as in almost everything he did other than Daito-ryu, was superficial.
Some would consider what he did an improvement on the original. I would not. (For another example, after the 2nd WW, he asked Sugino to teach him TSKSR spear. He could have learned from Sugino's teacher - but he did not want to be initiated and learn "properly") He just wanted to pick up something of interest to him that he could incorporate into his own practice - and doing so from his own student made it safe - he would thereby owe nothing to the ryu. He wanted to dip a toe in - not swim.
Note: There's nothing more to say here, Erick. Unless you have a primary source (not a website of non-practicing, "web-experts") which establishes some of what you are asserting, I've got nothing more to respond.