A decade after the events of xxxHOLiC Shunmuki, a melancholic Kimihiro Watanuki has taken over the shop formerly run by the mysterious Yuuko, fulfilling a promise he made to her. His companions Maru, Moro, and Mokona live with him in relative contentment, and some familiar faces drop by from time to time: former rival turned steadfast friend Shizuka Doumeki, and the former psychic prodigy Kohane Tsuyuri. While Kohane studies folklore under Doumeki at university, they encounter a case that is perfect for the master of the shop. Eventually, Watanuki receives a visit from Doumeki's grandfather, Haruka. He requests that Watanuki investigate his grandson's dreams. While inside the dream world, he discovers how their past adventures played out from Doumeki's point of view, leading Watanuki to uncover truths from 10 years ago and secrets about the ties that bind their friendship.