"The so-called wondrous Librarium is full of crap"
Professor Estella McKenzie (エステラ＝マッケンジー), also known as Emma or Agent E, is a instructor at the Military Academy for the Novus Orbis Librarium. She is a strict but fair teacher, and is in contact with Kagura Mutsuki, presumably being a member of his rebellion.
Estella is a toned woman with golden blonde hair and dark blue eyes - she has a black mole under her left eye. Her white staff jacket is revealing, showing off her cleavage and navel; the jacket is sleeveless with a white collar and small red tie worn around it, and the jacket itself reaches down to her upper calves. Estella wears a short blue skirt, black tights, white gloves, and NOL boots with stilettos.
To most students, Estella comes off as strict and with a legendary wrath. To keep up with appearances, her own room is filled with multiple pieces of athletic equipment, but underneath this, she is much softer and traditionally feminine than others would be initially be led to believe. She collects many different outfits with frills and laces, having a hidden room dedicated solely to her hobby.
Estella is fair to her students, only dishing out punishments where it is deserved. She keeps up with her students, being aware of the infamous "death dinners" and even has its consumption as punishment.
Powers and Abilities
Although not shown in combat, Estella is one of the more advanced users of Ars Magus, having been chosen by Cypher to have Ars Magus drained out of her. She seemingly engages in regular physical exercise given the equipment in her room.