Measurements: 84-55-83
Yui is a special mage, as she can only communicate with others through dreams. She also lives in the dungeon underneath the academy. After she was rescued by Arata and other Trinity Seven members (except for Lieselotte due to her disappearance) Yui can return to a normal life with other people and Levi as her close friend. She has a little sister character and is so close with Arata that she treats him like a big brother. Yui is a member of Trinity Seven too.
(Source: Trinity Seven Wiki)