"xxxHolic" centers on Kimihiro Watanuki, a high school student plagued by the ability to see spirits and supernatural entities, which disrupts his daily life. Seeking relief, he encounters Yūko Ichihara, a mysterious and powerful witch who runs a wish-granting shop. Yūko offers to help Watanuki in exchange for his servitude at her shop, where he must perform various tasks, often involving supernatural clients and their peculiar requests. Through these interactions, Watanuki learns about the complexities of human desires, the consequences of wishes, and the intricate balance between the spiritual and human worlds.

The narrative explores themes of fate, morality, and the interconnectedness of lives, often intertwining with the events of CLAMP's parallel series, "Tsubasa: Reservoir Chronicle." Watanuki's journey is marked by his relationships with key characters, including his classmate and rival Shizuka Dōmeki, who possesses spiritual abilities of his own, and Himawari Kunogi, a kind-hearted girl whose presence seems to bring misfortune to those around her. As Watanuki delves deeper into Yūko's world, he uncovers secrets about his own past and the reasons behind his spiritual sensitivity.

The series blends episodic storytelling with an overarching plot, balancing supernatural mysteries, emotional depth, and moments of humor. Yūko serves as both a mentor and an enigmatic figure, guiding Watanuki while maintaining an air of detachment. Her cryptic advice and the shop's peculiar rules often lead Watanuki to confront moral dilemmas and the unintended consequences of human wishes. The interplay between the characters and their evolving dynamics drives the narrative, culminating in revelations about their shared destinies and the true nature of Yūko's shop.

"xxxHolic" is characterized by its atmospheric tone, blending the eerie and the whimsical, and its exploration of the human condition through the lens of the supernatural. The series maintains a focus on the consequences of choices and the inevitability of fate, creating a thought-provoking and immersive experience.