Fred's piece; excellent and most to the point of our/your interest.
You have this.
The Spiritual Foundations of Aikido by William
$13.97 at Amazon. The author is a 6 DAN under
Saotome and teaches in Massachusetts. I've been to
one of his seminars and it was excellent.
The Philosophy of Aikido by John Stevens $17.00,
The Essence of Aikido: Spiritual Teachings of
Morihei Ueshiba by Morihei Ueshiba, John Stevens,
Secrets of Aikido by John Stevens, $16.97 (All
The Myth of Japanese Uniqueness by Peter Dale
Antidote to Stevens. No misty eyes here. Probably have to ge it through interlibrary loan.
Allegories of Desire: Esoteric Literary
Commenatries of Medieval Japan (Harvard-Yenching
Institute Monograph Series) by Susan Blakeley
Original Enlightenment and the Tranformation of
Medieval Japanese Buddhism (Studies in East Asian
Buddhism, 12) by Jacqueline I Stone
These last two discuss esoteric hermenuetics; my tentative
hypothesis is that KOTODAMA partook of this.
Also, search this lady's pages, she's written scholarly articles on the topic. I got mine through ILL.