Shiro-Uneri 白溶裔, しろうねり- [Yokai | Tsukumogami] - aka: “white undulation”
• About this Yokai: An ancient tattered cloth, towel or stripped kitchen rag left to rot in dirty, humid conditions, particularly in abandoned or uninhabited places, until it came to life as a tsukumogami; twisting itself into the shape of a tiny dragon. It flies about at night, harassing maids & kitchen crew and wrapping its slimy body around their faces, causing them to pass out! It has been known to suffocate those without any virtue or morals to death!
• Origin: Another Tsukumogami earliest explained by Toriyama Sekien in his "Gazu Hyakki Tsurezure Bokuro" (1784). This dragon towel appears to be hanging to dry next to or perhaps emerging from a well bucket. Toriyama’s included entry & illustration goes as follows:
"Shiro-Ururi" appears in Essays in Idleness. This Shiro-uneri is an old cloth transformed. I wonder if there are other types. So I dreamed." - (Translation: Japandemonium 2017)

[Shiro-uneri as it appears in Toriyama Sekien’s Gazu Hyakki Tsurezure Bukuro vol. 1 (1784) - Image source: Smithsonian]
The “Shiro-Ururi” Toriyama references here is indeed included as the 60th passage of "Essays in Idleness" (1332) (titled in English translations as "Taro Mania"). However, the humorous passage is not about a dragon at all, but rather a monk named Joshin, a high ranking priest who loved ‘taro’ (yams or potatoes) so much that he spent his entire life savings & inheritance on them! He'd even eat them while doing sermons! At one point Joshin gives another monk the nickname of 'Shiro-Ururi' which sounds like a slight variation of “Shiro-Uri” or "White Melon" which is a pejorative meaning "handsome, but without much ability." So when Joshin is asked to clarify what he meant by calling the monk “Shiro-ururi”, he avoids causing offence by saying, "I have no idea, but if such a thing existed, I am sure it would look like that priest's face!” (To me, it sounds like he lovingly called him a “potato head!”)
The name of this yokai, "Shiro-Uneri", means "white undulation" and is seemingly in reference to how a rag flutters in the breeze or as to how a dragon's slender body might move as though it was swimming through the sky! It seems like an odd choice to make a dragon based off of a story about a potato manic monk calling another monk Melon Head but Toriyama really liked tying his yokai to literary references. Perhaps he thought of the yokai then had the idea of mentioning Shiro-ururi from Essays in Idleness as if it was a similar species of the same yokai just as a joke. Or perhaps it was the other way around and he got his yokai ideas by going through books of great literature and writing down what yokai puns he could make. Who’s to say?
So where's the suffocation/strangulation bit coming from then? Well, most of the popular lore regarding this tsukumogami in particular comes from stories originating from much more recent books & modern bestiaries. For example, Tohoku Kaidan (東北怪談の旅) by Rio Yamada published in 1974 contained many ghost stories which were supposedly collected from before the second world war. The short legend which was included there was titled "The Revenge of the Ancient Towel" (古雑巾的複仇) which details a ghostly murder in Iwate Prefecture:
"A feudal lord murdered his maid and fled; but just as he left his house, an ancient rag flew out in the shape of the ghostly maid's face! The rag covered the feudal lord; suffocating him to death!”
The story was soon quoted by Shigeru Mizuki in his early yokai encyclopedias where Mizuki compared the two as the same yokai and said that perhaps Shiro-uneri would also strangle bad people to death with its awful mildewy stench. From there, the yokai made several appearances in anime adaptations of his manga, Gegege no Kitaro. Today a bronze statue of Shiro-uneri can be visited on Shigeru Mizuki Road, Tottori prefecture.
Shiro-uneri and Shiro-ururi might not be different types of the same yokai but there are other types of 'possessed or vengeful cloth/clothing Tsukumogami" which were also covered by Toriyama Sekien including:
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Jatai (蛇帯) a kimono sash that acts like a wriggling serpent, it suffocates those sleeping.
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Kosode-no-te (小袖の手) a Kimono with ghostly arms in its sleeves
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Hatahiro (機尋) The vengeful spirit of a jilted woman who came back length of cloth from her loom to take revenge on her former husband.
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Boroboroton (暮露暮露団) a ragged futon blanket come to life.
One other yokai that isn’t covered by Toriyama but is also a cloth that allegedly strangles people is ittan-momen. (another of mizukis favorites)

[Art sticker & writing by @SamKalensky (yo, that's me!) Editing by @Cattype. Part of my Hyakki Yagyo Night Parade of 100 yokai sticker series. Follow & check my shop out for many more! Thanks for your support everyone! another yokai next week<3]