Yuuko's time flow finally starts moving again. After being alive for an unknown number of years, she must depart now since she can't be held by the world of the living any longer. In her last moments, she faces Watanuki and makes her final wish: "Stay alive". In response, Watanuki makes the promise to remain in the shop of wishes until they meet again. Many years later, he still keeps that promise and performs the duties of a shopkeeper, granting wishes of those who come to him.

Source: ANN

Note: The first episode was bundled with limited edition copies of XXXHOLiC manga volume 17 (originally announced for release with the 16th manga volume), and the second episode with the limited edition of volume 19, which was also the last volume of the manga.

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Prequel: xxxHOLiC Shunmuki
Same setting: Kobato.
Same setting: Gekijouban Blood-C: The Last Dark