Chapter One: Why 'Puella Magi?'
It amazes Kyubey sometimes how little humans question things, if he could feel such a thing as surprise. They go about their lives never questioning anything when they really ought to. They show a truly remarkable lack of curiosity. The young females with whom he contracts are just a prime example of the ignorance of humankind.
There's the Irregular, Akemi Homura, who doesn't seem to be at all interested in finding out which gender Kyubey subscribes to and simply refers to him as an "it." There's Tomoe Mami, who doesn't bother to ask if she can make her wish to bring her parents back as well. There's Sakura Kyouko, who didn't think to consider whether her father would respond positively to the effects of her wish. There's Miki Sayaka, who didn't consider that anonymously healing her little crush's arm wasn't going to change his feelings towards her. There's Kaname Madoka, who doesn't bother to ask why Akemi Homura is so intent on her not becoming a Puella Magi.
It's amazing how few questions they ask about their own lives, and the whole process of becoming Puellae Magi. I would have thought that they would have at least asked me about the name.
Upon being given his marching orders, Kyubey was assigned to the nation of Japan and told that, so long as he met his quota, he was to be given free rein to meet his quota however he saw fit.
No Incubator will tell those whom they contract with any more than is absolutely necessary, unless the girls who agree to the contract have questions that can be answered. They will be told exactly what they need to know, and nothing more. All these young females need to know is that they will contract to fight Witches in exchange for a wish granted, any wish that they like. They will know that they must regularly clean their Soul Gems with the Grief Seeds they take from defeated Witches, and that if they do not, the consequences will be dire. Unless they inquire further, that's all Kyubey tells them.
Kyubey is not a fool by any stretch of the word. He suspects that if the young girls who become Puellae Magi knew that they were doomed to become Witches before contracting, he would not be able to meet his quota. Therefore, steps are taken.
Using the words that he does is not deception by the standards of the Incubators. It ought not to be deception by anyone's standards, regardless of what these young girls think. Latin is truly such an elegant language, and calling them "Puellae Magi" gives the whole thing an air of mystery and the fantastical that Kyubey knows from experience is highly appealing to his target audience.
If he uses "mahou shoujo", a reasonably intelligent girl wouldn't take long to make the connection with "magical girl" and "witch." Using Latin instead, even Latin that is not quite grammatically correct to translate into "magical girl", they look upon this as being just like something out of one of the television shows they seem so obsessed with. And indeed, if any of the girls he meets knows their Latin, "Puella Magi" ought to make sense, properly translated as "the sorcerer's girl", or, in a stretch of the language "girl form of the sorcerer." It will all make sense if they just think to ask.
It's not deception, Kyubey thinks, in response to all of the accusations he has ever received in the past. All they have to do is ask. I would tell them readily, if they asked. If they do not, that is their own loss.