Loving those series, but it always pulls me put of the story when they suddenly measure things in tatami mat sections; I mean... nobody in any world uses that, except on the islands of Japan.
And Japanese measurements before they went metric? Same as everybody else: a foot (called "shaku," but it is basically slightly less than 12 inches... just like a Japanese foot is to a European foot... just as the "meter" is the same as a "pace" which is a little under a "yard."
Every medieval society used their lower appendages for measurements, so jeez... why the tatami room measurements?