Yuki is a minor caracter seen throughout the Mahora Festival Arc. She is most often seen with her best friend Haruki.
Mahora Festival Arc
In Volume 10, Yuki and Haruki were one of the couples Negi saved from Mana's knockout bullets. She is then seen confessing her love to Haruki, although it is unknown if she was successful.
In Volume 14, Yuki and Haruki were one of the couples in the 'Mahora Festival Best Couples Awards', Where they cosplay as Little Red Riding Hood and the Wolf. They later win, due to Ako not wearing a 'skimpy' swimsuit, which got much less reaction from the audience.
In Volume 16, Yuki and Haruki were participants in the round game, and were hit by the 'Naked Ray'. Haruki asks her if she is OK, but instantly recoils due to Yuki being stark naked. He is comically kicked away by Yuki, while she yells, 'Don't Look!'.