Muto-shin is a deity which appears in Somin shorai setsuwa (anecdotes of Japanese old stories). He is also called Mutafu no kami or Muto tenjin. He made his first appearance in 'Enokumanokuni Tsuyashiro Shrine' according to the "Bingo no kuni Fudoki Itsubun" (regional gazetter for Bingo Province (a lost writing)), which was quoted in "Shaku Nihongi" (annotated text of the Nihon Shoki) written by URABE no Suetake in the late 13th century.
Mutafu no kami was a deity of Hokkai (Northern provinces), and when he visited Nankai (Southern provinces) to look for a wife, he said: 'I am a deity called Susanoo.'
He is therefore regarded as the same as Susanoo (a deity in Japanese mythology).
It is considered that "muto" is not a pronoun but refers to a deity enshrined in a sanctum of trapezoidal shape called "mutan" in Korea.
In Korea, there is a shaman-like presence called "mudang" (written as 巫堂). In China, there is a word "mudan" (written as 牡丹).
Also, one theory has it that Muto-shin is related to Takuto-tenno, a deity of Taoism syncretized with Bishamonten by Risei, Li Jing (571 - 649), a warlord in Tang Dynasty.
The anecdote of Muto-shin in "Bingo no kuni Fudoki Itsubun" later expanded into "Gion Gozu-tenno Engi," a narrative of Gozu-tenno (a deity said to be the Indian god, Gavagriva).
Muto-shin's brother, Konjin, became Kotan-daio (or Konjin) of Yasha-koku Country, and Muto-shin changed into Gozu-tenno, 'a giant of about 2.27 meters; a prince with the head of a cow,' and triggered a war against Kotan-daio. Gozu-tenno became the daio ("great king") of Rajagrha, Magadh.
It is written in "Irohajirui-sho" (a dictionary written by Tadakane TACHIBANA in the Heian period) as follows. There was a place called Kissho-en in the Kuso-koku Country in the northern part of Tenjiku (India), and Gozo-tenno, also known as Muto Tenjin, was the daio of a castle there'. It was written that Muto-shin had Hachioji (eight princes of Muto-shin) and 84,654 kenzokushin (ancillary deities).
According to 'Hokinaiden,' which is one of the scriptures of Onmyodo (way of Yin and Yang; occult divination system based on the Taoist theory of the five elements), Muto-shin was the reincarnation of the deity of Tengyosho (God of Heavenly Punishment), and was the daio in Rajagrha, Kisshoten (Laksmi), and was called Shoki-tei.
Kuso-koku Country' (written as 九相国) is sometimes written as 倶相国, 吉相国, 豊饒国, etc., but they all mean the same thing.