xx Hol ic ▁and ▁T sub asa : ▁Res er voir ▁Chron icle ▁Y ū ko ▁is ▁introduced ▁in ▁x xx Hol ic ▁as ▁a ▁w itch ▁who ▁runs ▁a ▁shop ▁that ▁gr ants ▁wishes ▁to ▁customers ▁in ▁exchange ▁for ▁something ▁of ▁equal ▁value ▁to ▁the ▁wish . ▁Y ū ko ▁takes ▁anything ▁from ▁pre cious ▁objects ▁to ▁abstract ▁concepts , ▁such ▁as ▁love ▁or ▁luck , ▁in ▁exchange . ▁In ▁the ▁series ' ▁start , ▁she ▁h ires ▁te en ager ▁K imi hi ro ▁Wat anu ki ▁as ▁her ▁assistant ▁so ▁that ▁his ▁work ▁will ▁be ▁his ▁price ▁for ▁grant ing ▁his ▁wish ▁of ▁protect ing ▁him ▁from ▁y ok ai . ▁She ▁is ▁usually ▁free - sp ir ited ▁and ▁somewhat ▁imm ature , ▁drink ing ▁constantly ▁and ▁forcing ▁difficult ▁tasks ▁upon ▁Wat anu ki . ▁However , ▁when ▁giving ▁customers ▁or ▁Wat anu ki ▁advice , ▁she ▁is ▁much ▁more ▁stern ▁and ▁offers ▁crypt ic ▁messages ▁that ▁serve ▁as ▁warnings ▁of ▁imp ending ▁danger . ▁She ▁constantly ▁speak s ▁of ▁in ev it ability ▁(" h its u zen ") ▁and ▁how ▁nothing ▁is ▁a ▁coinc idence . ▁ ▁Ac ross ▁both ▁x xx Hol ic ▁and ▁T sub asa : ▁Res er voir ▁Chron icle , ▁Y ū ko ▁remains ▁in ▁contact ▁with ▁the ▁te en ager ▁named ▁S ya or an ▁and ▁his ▁compan ions . ▁In ▁order ▁to ▁grant ▁him ▁the ▁ability ▁of ▁trav elling ▁across ▁dimensions ▁and ▁save ▁his ▁friend ▁Sak ura , ▁Y ū