A perverted lingerie stealing (once again a throw back to the typical manga male stock character archetype), chain-smoking, talking ermine, (though he has a long, and prehensile tail), that Negi freed from a trap when he was five years old. Since then, Chamo has been going to Negi whenever he ran into trouble.

Chamo cares strongly for Negi and will fight to protect him, but he is not above using him to try to make a fast buck. Chief among those methods is attempting to make probationary contracts between Negi and as many of his students as possible, since the act nets him 50,000 Ermine Dollars per contract.

Chamo often acts as Negi's trusty advisor in most things, though there are times his judgement and/or advice leaves much to be desired. He is skillful at analyzing dangerous situation and coming up with countermeasure when most of the others are in state of panic, but his plan usually have big flaws in it, a point that he often admits blankly. He is also quite good at analyzing individual strength and character, and puts them in good use during times of need.

He normally suffers Asuna's wrath whenever his schemes are discovered or he is caught in one of his perverted acts.

As a side note, being turned into an ermine is one of the punishments that Negi's magic academy gives, however Chamo is not a mage turned into an ermine, but actually a type of elf/fairy/Cait Sith (which he says he is very proud of).

(Source: Wikipedia)