Mieme

Beautiful woman whose real name, age, background, etc. are unknown at all.
She runs "Eyewear Shop Mieme" near the college where Yuu goes.
Strongly quirky personality. She has a habit of teasing people.
She can make magical glasses. When put on it, they bring out various abilities.
Her hobby is to travel around the world. There seem to be many acquaintances of sorcerers in the countries.

Source