Minako

Minako is one of MSF High's students that knows exactly how she arrived, but she is not willing to tell anyone the specifics.  The look that crosses her face when the topic is brought up is usually enough to tell someone that it's not pleasant, and your average student is polite enough to move the conversation to another place.  There are some clues to be had, though, namely her genetic similarity to specific earlier breeds of Demi-human, which suggests that she was one of the earlier lab-grown specimens, and given her mentioning that she's always been a Martial Neko, it seems likely that she was one of the original test groups, many of whom were worked to death and dissected to provide a measurable quantity of work output for potential clients.  Minako prefers to keep her mind off whatever it was that happened to her in her past, and in Mahou City there are plenty of opportunities to do just that.
Minako has a very forceful personality and this makes her an excellent mage, easily strong enough to fight in the battle arena, but she doesn't seem particularly eager to test her abilities in that capacity.  Instead, she has found another battlefield on which to compete, as a FenrisCo salesgirl.  While many associate the job title with sexy women, not always by choice, in skimpy outfits, Minako was a willing signup and as such is free to wear any outfit she desires, and thus prefers to stay in her usual school uniform or battlemage robes.  Despite what many would consider a severe handicap for a salesgirl, she astoundingly manages to have the third-highest sales in the company, right behind Nell and Miss Fenris herself.  This is attributed to her devotion to the job past that of the average worker.  While a normal FenrisCo girl might be able to lure in someone with their attractive appearance and snag a sale or two from someone too dumbstruck to bother shopping around, Minako goes to any length to help her customers or secure a sale.  Whether she's delving into a dungeon with a party to sell them healing items on the go, doing hours of library research on the mathematically perfect enhancement combos to have applied to a customer's favorite weapon, or outright challenging a more stubborn mark to a winner-pays-all duel, Minako is using her remarkable cunning and intelligence to gain lasting and big-spending customers.  Someday it's possible that she'll even overtake Nell as Miss Fenris's lead salesgirl, though she has no idea what she'll do once she reaches the top.
Through her various dealings with students, Minako has assembled a large pool of students and even citizens of Mahou City that owe her various favors, and she can call upon them at any pount to help her out.  In the case of a few students, they feel so indebted to her that they would follow her into any situation, and if she feels it will benefit her in the long run, she has no qualms with taking advantage of their friendship, though she is slowly learning that having them as friends is much more valuable than having them as business associates.