Self-Referencing: Yoshiro & Soh are the Goddess.

An otherworldly being that governs the people of the mountain from the heavens.

Soh is a messenger of the Mountain Goddess who guides and governs the world of chaos alongside Yoshiro. The two descended into the human world

The Japanese kanji doesn't use the word meaning to descend from heaven( 降臨:kourin) but it's obvious that it means heaven because this plaque matches Cursed Soh's plaque.
(old post on this: The statue of the Goddess + a Divine Heir)

The two are the descended Goddess.

Korin(光輪) is what Cursed Soh's wheel is called in the official merchandise. It's a homonym.

Kouhai(光背) is what it's called in the files. A Buddha/Bodhisattva halo, specifically.

It's likely Shingon Buddism. 

Yoshiro is a Buddha and is synonymous with the Goddess hence why she walks the Path of the Goddess.

To further elaborate on this descent, the halo is the Goddess emblem which we see when Yoshiro and Soh purify the gate:

Yoshiro's vocals('ooooooo') during the kagura could be the sound a priest makes during a ritual to signal the God is descending. We see this symbol during the ritual. The 'korin'. The Goddess descending: Yoshiro and Soh purifying.

As Yoshiro crystallizes, her vocals disappear from the purification music. Because she becomes the Goddess, there's no need for her to declare the Goddess is descending. She is already here now, almost ready to be enshrined.

(will update with the youtube video showing the music differences)

This phase is where she is likely already the Goddess because she's able to affect Cursed Soh. We also receive 'Birth of a Goddess' when she reaches this stage of petrification.

We see Birth of a Goddess at the true ending, too.

Birth of a Goddess

When she begins her petrification, it's at the place where the Goddess is said to have descended: Kamukura Shrine(神座神社かむくらじんじゃ). 

Kamukura. A place where a divine spirit resides.

Kagura (神楽かぐら, "god-entertainment") is a type of Shinto ritual ceremonial dance. The term is a contraction of the phrase kami no kura ("seat of god"), indicating the presence of gods (kami) in the practice.

Yoshiro is a Kagura maiden. A literal vessel for the Goddess. The divine body of the Goddess must be replaced periodically.

The pact: a Maiden needs to become a vessel for the Goddess, her body used as a katashiro to cleanse the mountain.

But why say Yoshiro descends from heaven? Possibly because 'Yoshiro' is the nigitama of the Goddess.

The Maiden and 'Yoshiro' are different. Otherwise why not simply use her name each time she is referenced? Once she becomes the chosen Maiden and embodies the benevolent side of the Goddess, she is called Yoshiro.

Her plaque is strange though. Why would she worship the ancestral deities? It would fit to call her 'The Maiden' so I don't quite understand. Unless we're meant to acknowledge she is the final Yoshiro and now has that name?

Soh is a wakemitama/bunrei/divided spirit of the Goddess.(So she is the Goddess) Likely the Aramitama, but that is also Cursed Soh. 

Soh's plaque contains information about Yoshiro and bind the two together.

Cursed Soh's commentary never addresses the resemblance to Yoshiro. Instead, it only speaks of capturing Soh's likeness in reverse because Cursed Soh is a mirror. Her clothes are meant to be 'white ritual robes where light is trapped within, reflecting forever in the mirror'

Shintais are often mirrors. The mirror that the Goddess is trapped in is the body of a Maiden which also houses the impurity?

Yoshiro has a bronze mirror on her with 24 circles. A shrine maiden's garb is white and red. And of course, there's this anomaly:

May I add that in old posts(A perspective on artwork of the Maiden and Messenger, The Maiden in the artwork and Soh's face), I suggested that when we look upon Yoshiro's face, we're meant to be looking at Soh's face as well.

why are her eyes so much darker?

The artbook proves I was right but it wasn't implemented. Or it's better to say Yoshiro's face was changed.

In the normal ending. Yoshiro ascends to Godhood, becoming the Goddess, and meets Soh, her messenger/divided spirit/self who then disappears.

In the true ending, Yoshiro is spared from this fate and remains on earth. The pact is broken and we have eternal sunlight.

Question is...how was it broken? Soh reabsorbed all her trapped power but why did she break the pact? To prevent the same outcome? But what about the impurity?

Human sin never wanes no matter how many nights pass, but to walk among the endless shadows is to be human.

人の世の罪は、幾夜いくよを経て尽つきせぬものなれど断ち切れぬ陰かげと共に歩むもまた人の世か……

Normal ending dialogue. Hinting at the acceptance of impurity in life? 

畏哭いこくis Seethe in Japanese. Ikoku. Wailing and lamenting.  Very different to the word 'Seethe'. To face sorrow is part of life. Could that also be the meaning here?

 The true ending: 

And so concludes the battle fought across generations.The tale lives on for the telling, to be celebrated as a ceremony for ages to come.

 幾度いくどもの世代せだいを繰くり返した戦いはこれにてお仕舞しまい物語は風習となり語り継つがれ祭祀さいしとして後世へと続いて行く.

Yoshiro's name is read as 'generations' here. Many Yoshiros have passed. 7 in total. 

Cursed for 7 generations. 

Is the Goddess inspired by Inari? Or perhaps a mixture of Inari and Konohanasakuya-hime?

Is it a Dakiniten /Inari situation? The Dakini, after being purified by the Buddhist counterpart of Amaterasu(Dainichi Nyorai), became the deity Dakiniten.

Dakiniten is said to be a manifestation of Amaterasu, likely the result of this purification.

Inari is a Kunitsukami. Amatersu is an Amatsukami. The lines between these two categories eventually disappeared through worship, according to Kunio Yanagita in his 'Mountain Lives':

The Jingiryō of the legal codes preserves the names heavenly gods and earthly gods; down to the time of Wamyōshō, the earthly gods were read as kunitsu-kami or kunitsu-yashiro. But these two alike were to be worshiped by the Jingikan according to the regular rites, and by the Nara period the spiritual lives of the old and new peoples may be recognized as having fused without remaining trace. The register of deity names in the Engishiki, while including many gods clearly known from their names—such as kunitama and kōritama—to belong to the gods of the land, no longer even preserved the distinction between heavenly gods and earthly gods.

Kunitsuyashiro (国津社 or 国つ社).

A little on 'kunitsu-kami' from the book:

It is transmitted that when the ancestors of our great sovereign first arrived on these islands, there were already many earlier inhabitants in the land. In the ancient records, these are named kunitsu-kami, “gods of the land.” 

This is about actual people however so it's not helpful. But it did remind me of the Maiden's ancestors cultivating the land and making a promise to the Goddess. 

Could the Goddess actually have once been a local woman? ...

(I guess not since there's magic and Seethe.) 

But...

"...people and gods, gods and Seethe, and misfortune and fortune are two sides of the same coin." according to Capcom.

There is another Goddess that appears very important: Seoritsuhime, the mysterious Goddess of purification. Said to be the aramitama of Amaterasu and her consort when Amaterasu is male.

Chozuya that feature dragon ornaments such as this are  referencing Seoritsuhime. Dragons and purifying spring water from mountains are her symbols.

Perhaps I have it wrong on the 'mitama'.

Soh & Yoshiro are the nigitama of Amaterasu.

Cursed Soh is the aramitama of Amaterasu, the Goddess of Purification Seoritsuhime.

There are a few Goddesses that could have served as inspiration. I'll touch on them in the next post.