Googling about for info reminds me that the stupendous happenings of vol 8 were signalled as far back as vol 1. Thus I must reread vols 1-4 to see what else I've forgotten and what further hints may have been dropped about this and that and *mostly* the structure of the Mito clan, which I know I'm not going to be told. I was hoping for a leeetle more information on who the hell Waki is anyway and didn't get that either. Still, a very satisfying read; I wish there were more manga that could hold me like that.
Also, any similarities to West End and 12 Kingdoms are doubtless totally in my imagination.