She works as the librarian incognito at the girl's school. The girls in the library are always crowded around pictures, or a boom box talking about or listening to Kyouta. Yui seems interested in Kyouta, but still lectures her students to keep quiet and not enjoy his music in the library.

She wants Kyouta for his powers and is an important member of Wiz-Dom. She manipulates Asumi to gain influence over Kyouta's future. Lemon is her apprentice.