She is the boss amongst spiders, since they're her kin. She has a nasty aura capable of poisoning a pure spirit, and she can pull up a spiritual barrier which is why the Tengu can not enter.   She's the one who kidnapps Zashiki Warashi and ate Watanuki's eye. She hates people who do not appreciate what they have and want to sacrifice themselves. After teaching Watanuki a lesson on that and eating his eye, she lets them go. She is an interesting creature since we can't be sure sure if she is good or evil. 

Kimihiro Watanuki is haunted by visions of ghosts and spirits. He seeks help from a mysterious woman named Yuko, who claims she can help. However, Watanuki must work for Yuko in order to pay for her aid. Soon Watanuki finds himself employed in Yuko’s shop where he sees things and meets customers that are stranger than anything he could have ever imagined.
 
(Source: Kodansha USA)
 
Notes: 
- The series was re-named to xxxHolic&bull;Rou on chapter title pages of chapter 186 and on, but not on their volume's front covers, spines and indicia. 
- The chapter count contains a one-shot published in May 2010 to commemorate the switch, which was later collected into Volume 18. 
- The chapter count also reflects the magazine releases; the chapters plus the one-shot were re-arranged into 109 chapters across 19 volumes.

Still working to get his wish complete, Watanuki finds himself into more mess than he can handle when certain facts about his everyday life gets revealed and when he needs to learn the lesson of Yuuko the hard way.
 
(Source: Anime News Network)

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