The Pipe Fox
Let me start with the story how the pipe fox came to be known in the story of xxxholic, and it all started with Ame-Warashi coming to the shop and wanting something to be done for her. Or better the story starts with some creepy arms growing like they were flowers, and that creeps Watanuki as all the things that happen in his life. Anyway, Ame-Warashi asks for help, not for her but for hydrangeas that are suffering from something, and Watanuki and Doumeki are sent to investigate, to find out in the end that the blush of flowers was trying to show, by the change of color, that under it there was a body of a missing child. Because they managed to have the mission done, it meant that their part of the contract was done, so Ame-Warashi had to come with her part of the payment, and she gave a pipe, neatly made and the form was of a small long fox.
The description on the page 77 of The Official xxxholic Guide says:
Pipe Fox Spirit - A spirit somewhat like a familiar, that Yuuko recived in exchange from the Ame-Watashi. It can elarge itself and fight evil spirits. It likes Watanuki because of his ability to sense those spirits, and so sometimes the pipe fox will sneak into his clothes to go to school.
We do see the Pipe fox finally in action in the Volume 5, during the chapter dedicated to the Girl controlled by wings. It all starts with the fact that the pipe fox sneaked in Watanuki’s clothes and went to school with him. It find a feather and that set off a chain of events that leaded the main character in trouble (as Yuuko says – hitsuzen). The story goes with the fact that Watanuki spots a girl in school that has small weird wings on her back, and from her a feather arrives. When he showed it to Yuuko she warned him and destroyed it. During the chapter we see the girl getting angrier, and taking her anger on those around her, while the wings grow, till the moment she attacks Watanuki and Doumeki, and the wings finally detach from her and try to hurt Kimihiro, but from his shirt there is Mugetsu to the rescue, transforming in to it’s bigger form, a nine-tailed fox (also known as kyuubi in the Japanese folkolore) attacking Ko (that kind of wings, check glossary for more on them) fighting them and in the end destroying them with its purifying fire.
-more information will be added soon