2. Both Minakata and Ueshiba were sons of local merchant families whose religious association was Shingon, very likely the same temple. Additionally, Minakata's work on Kashima Island from 1904 forward brought him into direct contact with the same fishermen whose interests Ueshiba was advocating in 1901. It is a virtual certainty that Ueshiba would have known who Minakata was and likely that Minakata would have known who Ueshiba was, and it is within the realm of possibility that the two men met before Ueshiba's military service in the Russo-Japanese conflict.
A couple more comments.
Kisshomaru goes into some detail about the large number of Shingon temples in Tanabe. This has been translated and appears on pp. 55-56 of A Life in Aikido
. He distinguishes between various Shingon sub-sects and the Jizo temples that practised Ryobu Shinto. It seems that Ueshiba started his schooling at such a temple.
Secondly, Kisshomaru notes that Ueshiba may well have met Minkata before he went into the army. The statement appears on p. 76 of 『合気道開祖植芝盛平伝』: