豊延 Hironobu.【追儺 Tsuina Ceremony 】15

Mutsu means the back part of the present Tokaido Highway and Higashiyama Road.
The four prefectures of today's “Aomori, Iwate, Miyagi, and Fukushima
It refers to the entire Tohoku region.
In the time of this animation, it is “Michinoku”.

Hitachi is the name of the old country in today's Ibaraki Prefecture.
Shinta-gun is in the information in “Fudoki”,
Shinta-gun is the area around the current cities of Ryukesaki, Tsuchiura, and Ushiku.
(The “Fudoki” is a book written in 713, which is a collection of folklore
from various countries, some of which has been scattered.)