xxxHolic, Vol. 15 by CLAMP, William Flanagan (Translator)

Kimihiro is having some wish-granting success with his very first customer, but his efforts are interrupted by a disturbing dream of the witch Yuko vanishing forever. Even people Yuko has helped are saying they've never heard of her. Too bad there is no such thing as "just a dream" in Kimihiro's universe. . . .
xxxHOLiC crosses over with Tsubasa, also by CLAMP. Don't miss it!