Much of the discussion concerning the relationship of Minoru Hirai to Morihei Ueshiba can be found in an interview conducted by Stanley Pranin, of Aiki News / Aikido Journal. I think the issue was No. 100 and subscribers to Stan's AJ forum can read the entire interview.
Salient points of the interview include:
Hirai trained in the martial arts long before he met M Ueshiba;
The Dai Nippon Butotokai aimed to organize all martial art as part of the war effort;
There were moves to include aiki-budo (i.e., general jujutsu), but the name had to be such that judo and kendo would not object: aikido was decided on as the least offensive name: calling the art a DOU was also a plus, in view of the spiritual connotations;
Hirai was Soumu Bucho (Head of the General Affairs section) of the Kobukan Dojo.
The article was originally conducted in Japanese and then translated. I have all the other articles published by Stanely Pranin, in Japanese and also in English. They are good translations, but still translations. For example, 'Soumu-bucho' has a nuance that is difficult to convey in English.
My take on the interview is that Mr Hirai's assistance to Morihei Ueshiba was primarily of a political nature, for he was well connected. Considered overall, I think it is fair to say that the relationship of the two men with aiki-budo / aikido was quite different.
Best regards to all,
Peter Goldsbury,
Forum Administrator,
Hiroshima, Japan