Encounters with the tengu (mountain demons) are a recurring theme in Shotokan's Secret, Expanded Edition.
The samurai training schools (the bugei ryuha) all had a foundation myth. The founder of the school retreats into the mountains and becomes a yamabushi, a warrior hermit. He devotes himself to his training, forsaking all worldly interests, while praying for inspiration. After years of training, a tengu (a flying demon) takes pity on him. (In Japanese art, the tengu look a lot like the Flying Monkeys from The Wizard of Oz.) See the image of a tengu here.
The demon comes in the dead of night to whisper secrets in the master's ear. These secrets become the foundation of the new martial art.
I identify with those ancient yamabushi with their terrifying nightmares. I live in the Sierra Nevada mountains of California. I do kata in my sleep, much to the annoyance of my wife. I often awaken in the middle of the night with some new inspiration hot on my mind. Was my subconscious at work on the problem as I slept? Or was I visited by a tengu who whispered a secret in my ear? I don’t believe in demons, but that doesn’t seem to matter. They talk to me anyway!
Many of the kata interpretations detailed in Shotokan's Secret, Expanded Edition came to me in nightmares that I shudder to recall. In one I beat a samurai senseless with his own helmet, which was the key to understanding heian yondan. These nightmares were as frequent as they were intense.
But now the book is finished. The mad year of writing, photographing, and revision is finally over. It is out of my hands, now and forever.
And the nightmares have stopped. I'm sleeping through the night for the first time in ages.
Don't ask me what it costs to write a book like Shotokan's Secret. The cost is high.