From The Heretic Knowledge Vault
Little is known about Kureji, since she's not appeared in the actual comic and possibly only exists in the Fun with Familiars continuity/omake. She first appears in this comic, where she is working on her plan for revenge against "those jerks at Sashi Mu" who got her kicked out. She seems to have a micro-unicorn familiar with the oh-so-cute name "Mr. Snugglesworth."
The full details leading up to her expulsion have not been revealed yet, but according to her classmate and fellow exile Rokku, their mutual expulsion is all Kureji's fault. The version of her in the Errant Road game (see next paragraph) claims to have graduated second in her class from the "Suchu Dentoapashi Community Mage College," whatever that is.
A version of Kureji also exists in the Errant Road free-form role-playing game. She's introduced in this entry in the Forum. Viking-Sensei's notes there make it clear that there is some degree of continuity between the omake and the Kureji we've all come to know and love in Errant Road, where, it is fair to say, she has something of a reputation...