Fascinating. Katori Shinto Ryu is famed also for having a (anti)ninjutsu oral tradition. As an aside to this discussion, I've noticed that some of the very oldest ninjutsu image representation have ninjas holding the hand position in the 7th (Retsu?). If kuji/Juji is not specific to ninjutsu but adopted by them, why does the 7th seem paticulary associated in iconography with ninjutsu? I seem to remember a really old interview where hatsumi is quizzed about this by a young Japanese lady, and her first immediate hand position was The 7th. The works of Gingetsu Itoh seem to emphasise it as well. Any takers?