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.
The longer Watanuki resides over the shop, the stronger he gets and the more he learns to rely on his friends in the way his friends have relied on him. But as his powers grow with the passing of years, his memories of Yûko also grow distant. Will the current shop master ever be reunited with its former owner and will Watanuki ever be able to leave the shop? Find the answers to these questions and more in the final omnibus of xxxHOLiC.