A week before his death, Miyamoto Musashi, author of A Book of Five Rings, created the twenty-one principles of Dokkōdō, "The Path I Go Alone." Three hundred fifty years later, Gregor Fjellrev was born. At fifteen, Fjellrev read A Book of Five Rings, in secret, for the first time. At twenty-two, he rededicated himself to the Path as described in that work, later learning of Dokkōdō and exploring it at the age...