If you haven't already tried these authors, Jonathan Clements and Andy Cummins are both pretty good, although obviously not Japanese themselves.Since we're about to head to the library, I'm looking up non-fiction books on feudal Japan/samurai in general; because I can only trust so much online data, and because it's easier to separate fact from fiction (fun as the latter is) in physical book format.
Why I feel the need to research something not intended for my writing projects, I couldn't tell you--beyond sheer curiosity. And perhaps the possibility that one or two things might make it into Arcane Guardian. Maybe. I dunno, yet. ._.