The fictional characters appearing in the manga and anime series xxxHolic were developed by Clamp, a group of four manga artists. The series takes place in modern Japan and focuses on various supernatural themes, with most of the main characters being humans with magical powers, supernatural creatures, or spirits. Published concurrently with Clamp's Tsubasa: Reservoir Chronicle manga, the two manga's plotlines and character cross over.
The series' protagonist is Kimihiro Watanuki, a high school student plagued by yōkai and ayakashi spirits. One day, when running away from the spirits, he accidentally enters the shop of witch Yūko Ichihara, who has the power to grant wishes for a price. Yūko decides to grant his wish of making his demons go away in exchange for having him work as her assistant in her shop. Working at Yūko's shop, Watanuki encounters various spirits and also gets to know his classmates Shizuka Dōmeki and Himawari Kunogi better. Although Watanuki comes to value his new life at the shop, he begins to worry about Yūko and eventually promises that he will try to grant her wish, should she have one.
The characters from xxxHolic were designed by Clamp's members Mokona and Tsubaki Nekoi. Some of their designs were inspired by ukiyo-e art style. The series' characters' interactions and personalities, as well as the designs, have been met with positive critical reception. On the other hand, the designs featured in the animated adaptations have received mixed reviews.