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"Huh? Oh, hey kid! Yeah yeah, I'm a cute bunny-fox, eat your heart out. Ack! Watch it! Wait! No no no you didn't do anything wrong! It's just been a super long time since a little girl actually hugged me, instead of kicking me out the window after summoning me, or try to eat me, or sic their dog or me.
"Mikey's as good a name as any to call me by kiddo. So how'd you get the pendant? ... Your dad bought it from a store in the shopping mall that wasn't there yesterday? That old man sure has a sense of humor. Look kid, I've been on a long string of bad days, so just bear with me. What am I EXACTLY? I'm a servant of a higher power. Call me a space alien, since people are more read to believe those exists than messengers of a Higher Authority these days. Apparently cute critters are more appealing these days than flaming eyeballs with a dozen golden wings.
"Ahem: so little girl, want to fight demons, yes, literal demons, not invaders from another universe, not Yokai, not things that feed off unhappiness... soldiers of Hell, straight up. In exchange you never have to grow up, you get to live forever (until you fall in battle), and you get obscene magical powers, a fancy magic weapon born from your own fighting spirit, and a very very pretty dress with lots of frills."
"NO! Little girls do not turn into demons when their magic runs out! Don't you think this line of work is horrible enough as is?! ... Please! Stop! Don't cry! I'm sorry! I've... Look... There, there, okay, that's a brave girl... I apologize. I was wrong to raise my voice like that.
"I can only grant my power to those who are still innocent and pure at heart, still believe the world, and humanity, are both still worth saving, that good can and should triumph over evil, and possesses female's natural stronger connection to the spiral of life than males possess. And I was summon by you touching the pendant, so that means you fit that criteria.
"No no no, it doesn't mean you have to be perfect or anything. You count as a good person, so you worthy of this power, and burden.
"Good news is, your soul is guaranteed to be 100% safe from the demons for accepting this burden of their own free will, and upon your death your spirit will be granted immediate entry into Paradise's Ninth Sphere... Uh, just trust me, that's a good thing.
"So what do demons do that's bad? They eat souls. And then it's like that person never existed. As an example, children are left as orphans in spite having a three bedroom house they can't pay for. Students don't find it weird they've had an entire school year without a teacher. People don't wonder how that airplane took off and landed without a pilot. And this makes them smell even stronger to the demons. And because they're not worth thinking about, no one writes it down, eyes roll over information on people who no longer exist, and it never makes the news that was anniversary party that day with no guests. One burden is that YOU, me, and any other magical girls WILL remember them.
"So why can't I fight them directly? Smart kid for your age. That means you'll get far. Because, my kind, and theirs, when we give an oath, we CAN'T break it, I can even comprehend the idea without knowing you humans do it all the time. The demons took an oath to Lucifer to remove all the imperfection God placed in the universe, IE, YOU, your parents, your entire class, your teacher, their families, everyone. When the divide happen, we were supposed to take an oath not to screw with mortals DIRECTLY... they simply declined to take it when we did. This isn't some promise I can break... it literally part of my BEING now as much you being aware of your own existence is yours.
"... what did you say? ... Kid you can't take this back! There's no retirement! ... You serious? Kid it's... it's been so long... most say 'there's too many people in the world anyway' 'what has the world done for me' or something like that... Fine. I, Mikey, Messenger of the Higher Power... recognize you, Mary, as a magical girl. ... Congrats kid. Hope you enjoy using chairs to reach the high shelves."