Having finished the book, I have a couple of comments. First, it's true that Rowland has included Japanese-folklore supernatural elements before - in The Assassin's Touch, in particular, but I think there was something in one of the earlier books too - but it was much more pervasive in this one. Since I read the books more for the peek into late-17th-C Japan more than anything else, having it shift towards what I would consider fantasy is offputting. Second, yeah, Hirata in particular reacted to the Ainu in what seemed an anachronistic fashion. (Having it happen after such a brief exposure is what bugs, I guess; perhaps there were Japanese who "went native" on Hokkaido, but that should be a slower process.)

I don't see characterization as one of Rowland's strong suits, in any case - she does things with POV that I'm uncomfortable with - so that doesn't bother me too much. Still, I'm not feeling particularly engaged with the series anymore.