XXXHOLiC follows a high school student, Watanuki Kimihiro, who is plagued by visions of ghosts and spirits. He encounters a mysterious witch named Yuuko, who claims she can help him stop the visions. In return for her aid, he must work in her shop and help grant the wishes of her customers.
Throughout the series, Watanuki meets various supernatural beings and helps them resolve their problems. As he does so, he discovers more about his own past and his connection to Yuuko's shop. Along with his friends Domeki Shizuka and Himawari Kunogi, Watanuki embarks on a journey to unravel the mysteries of his life as well as those of Yuuko's shop.