What I find compelling about Shinkage-ryū is that it sits at the head of a family tree most people know only by its most famous branch. Say the name Yagyū and a certain kind of reader will nod; say Kamiizumi Nobutsuna and far fewer will. Yet it was Kamiizumi who made the school, and the Yagyū inherited it. I like returning a tradition to the person who actually built it, partly out of fairness and partly because his story is, to me, the more interesting one.
He is also a relief to write about. So many founders of this period dissolve into legend the moment you press on them, and the honest paragraph has to begin by admitting that almost nothing can be checked. Kamiizumi is not quite like that. His dates are loose and the lineage behind him fades into tradition, but the man himself is reasonably well attested: a warrior of Kōzuke who lost his lord and took to the road, teaching as he travelled. When the record is this solid I feel I can relax a little and describe a person rather than a rumour.
The detail I keep coming back to is the fukuro-shinai. It is easy to walk past, a piece of split bamboo in a leather sleeve, but I think it is one of the quietly important inventions in the history of the sword. Before it, you could either drill forms in the air or risk maiming your training partner with a hard wooden sword. The covered shinai opened a third way: you could actually hit each other, hard, and come back the next day to do it again. Everything that testing makes possible, including the discovery that a technique you admired does not survive contact with a real opponent, flows from that simple idea. When I see kendō players in armour I think of Kamiizumi's strip of bamboo.
I am wary, though, of the stories that have gathered around him. The most famous is the tale of the swordsman who shaves his head, borrows a monk's robe, and walks unarmed up to a cornered madman holding a child hostage, only to seize the man the instant his guard drops. It is a wonderful story, and it is told of Kamiizumi, and I do not believe a word of it can be confirmed. That does not make it worthless. Legends like this one tell you what a school valued, in this case the idea that the highest skill is to resolve a deadly situation without killing, the seed of the "life-giving sword" the Yagyū would later make their motto. But a legend that teaches you what people admired is a different thing from a record of what happened, and I try never to let the two blur.
What I admire most is the shape of the art itself. Shinkage-ryū does not hand you a list of answers. It teaches you to read an opponent, to see the openings in his guard and his intention, and to draw him into moving first so that his attack becomes the opening for yours. That is a harder thing to teach than a catalogue of strikes, and a harder thing to learn, because it asks you to be patient and attentive rather than merely fast. There is something almost philosophical in it, a refusal to lead with force, and it explains to me why the school's later thinkers reached so naturally for the language of Zen.
If I have a reservation, it is the one the Yagyū fame creates. It is tempting to treat Shinkage-ryū as simply the prelude to the Yagyū story, a first chapter before the interesting part. I think that gets it backwards. The Yagyū were brilliant inheritors, but they inherited. The questions the school asks, about timing, about reading another person, about winning by drawing the other out rather than overpowering him, are Kamiizumi's questions, and they are good enough to outlast any one family's claim to them. That, more than the duels and the disguises, is why I think the founder deserves to be remembered in his own right.