Eritate-goromo - 襟立衣(えりたてごろも) - [Yokai|Tsukumogami] aka “High Collar”, “Standing Collar Clothes.”

• About this yokai: A monk’s high collared kimono that once belonged to the profoundly prideful King of the Tengu, Sōjōbō of Mount Kurama. Before he became a tengu, Sojobo was a human monk who became so conceited he mistakenly believed that he had attained enlightenment. And so, rather than ascending to buddhahood and reaching Nirvanha, he became a Dai-Tengu, persisting in his arrogance even in death.
After decades of being worn by such a powerful yokai, his robes came to life as a Tsukumogami. Its standing collar folded forwards resembling an origami beak, sharp proud looking eyes unfolded & leered from the robes shoulders. The back of the robe stood upwards, somewhat resembling a bird's tail feathers. It even sprouted a white, feathery beard, taking on an appearance similar to the tengu that who wore it. It wields a powerful, wind blowing hauchiwa fan to which all other tengu must submit. Perhaps these high-collared robes are as powerful and prideful as the tengu who wore them. And- if they’re anything like their straw cousins- perhaps they can even turn invisible! (You’ll read more about that in the “The Antique in Question” section below)
• Origin: The Eritate-goromo makes its earliest illustrated & named appearance in Toriyama Sekien's Gazu Hyakki Tsurezure Bukuro (1784) in which Toriyama depicted the empty vestment proudly sitting on a stage in front of a folding screen decorated with a spruce tree and clouds. The kimono stands upright and is holding a folding fan and a buddhist rosary and a lotus shaped incense burner at its feet. Toriyama's description of the yokai goes as follows:
"Eritate-goromo is the high collared vestment worn by Sojobo of Mt. Kurama, to whose feather fan all of the other tengu must submit, Buzenbo on Mt. Hikozan, Sagamibo on Mt.Shiromine, Hokibo on Mt.Oyama, Saburo on Mt. Izuna, Taro of Mt. Fuji down to the other Konoha Tengu. So I dreamed." – (Translation from "Japandemonium" 2017)

[Eritategoromo as it appears in Toriyama Sekien’s Gazu Hyakki Tsurezure Bukuro (vol 2). [1784] - Image source: Smithsonian]
• The Antique in Question: The kimono is called a “kyūtai” (裘代). It is a floor length kimono worn by high ranked buddhist priests for winter ceremonies. The tall, standing, padded collars are sometimes called "Sōgōeri" (僧綱襟). Being Sōjōbō’s robes specifically, it feels like a bit of a naming pun there-in and of itself!


[Kyutai robes: Kyoto costume museum]

[an illustrated example of similar robes]
Sōjōbō is often said to be the most powerful Tengu in Japan! (I've already written a lot about him here previously, so I won't repeat myself too much.) Dai-Tengu are considered some of the most powerful yokai with powers comparable to demigods. They can appear in dreams, speak without moving their mouths (telepathically?), as well as many other reality warping feats. Being the tengu king, Sojobo’s very often said to have the strength of a thousand tengu! So I’d suppose it’s only natural that after being worn by someone so powerful, Sojobo's ‘essense’ would rub off on his robes.
Tengu are often said to own magical items. Most famously, tengu are known to wield feather fans known as “tengu no hauchiwa” which they use to whip up storms (and also sometimes comically said to be used to grow noses.) Some tengu may have straw cloaks which allow them to vanish & become invisible! (see also: Kakuremino.) Unfortunately for tengu, despite being so powerful they can also be quite foolish and will often trade their magical gear to humans for mundane items. One fairy tale tells of a boy who tricked a tengu into trading him his straw coat of invisibility for an ordinary bamboo stick that he pretended to see far off lands with. There's a ton more stories like this one, but I won't cover them all here today.'
Admittedly, beyond Sekien’s entry there's seemingly no earlier folk stories (at least that I'm aware of) about Sojobo's robes coming to life so this yokai is likely another of his punny creations! Nevertheless, it's probably safe to assume that king Sōjōbō’s robes are as decked out in magic (& likely just as prideful and possibly just as powerful) as he is!
The other tengu listed in Toriyama’s description are the usual contenders ranked among the “8 most powerful tengu” which are said to be local to some of the tallest peaks in Japan! These eight tengu are as follows (though it often varies depending who/where you’re asking):
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Sōjōbō of Mount Kurama. – [x]
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Buzenbo of Mt. Hikozan. – [x]
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Sagamibo of Mt.Shiromine. – [x]
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Hokibo of Mt.Oyama. – [x]
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Saburo of Mt. Izuna. – [x]
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Tarobo of Mt. Fuji. – [x]
(X = links to Tengupedia’s list.)
These tengu’s names and mountains were also included in the Tengu-kyo (天狗経) a buddhist sutra which was thought to have been written sometime between the late Muromachi to the early Edo period. Supposedly, this list was chanted by Shugendo practitioners during their exhaustive hikes and prayers in the mountains. Supposedly the chant could be used to call the local tengu to dispel evil. The sutra is also a list naming the 48 most powerful tengu & the mountains they inhabit! It also mentions that there are “125,500 tengu“ which presumably live hidden in the mountainous regions across Japan! (You can learn more about each tengu named and listed in greater detail on Gabi Greves’ Tengupedia blog here. I’d also recommend browsing Toyoda Toki’s tengu blog. It’s in Japanese but they have a lot of very charming & fun tengu illustrations.)

[Tengu-kyo sutra from 1975’s Tengu Research “天狗の研究” by tengu folklorist, Mitsutoshi Chikiri (知切光歳 1902-1982)]

[Sojobo of Mt. kurama. Edo period print by Utagawa Kuniyoshi. (1798-1861) [image source]
[Art Sticker by @samkalensky (yo thats me!) editing by @cattype, part of my Hyakki yagyo night parade of 100 demons sticker collection. if you enjoyed this check the shop & support for many more ]