There is a sillhouette in the window.

...is that a cat? She gets up and walks over to the window to take a closer look.

It is not a cat!

Hello, it says telepathically.

...that is definitely not a cat.

"Hello?" she says back, out loud.

It trots back and forth along the windowsill like a cat that wants to come in. But is not otherwise a cat. May I come in?

The not-cat is talking in her head. It sounds like a person. Okay. This is probably the weirdest thing ever to happen to her, but why not. She nods and opens the window, careful to stand out of the way of the blast of cold air that comes in as she does.

In it hops. It flicks its tail. Thank you!

"You're welcome," she says, quickly closing the window once it's inside. "...Who are you?"

My name is Kyubey! What is your name?

"Shania. How are you talking in my head like that?"

It's magic that I have because I can't speak out loud. You can do it too, with me! You're a little bit magic.

Huh. She's not totally sure how to do it, but she tries to send her thoughts to Kyubey. Is this working?

Tail-flick. Yes!

This is so cool. She flops back onto her bed with a big grin on her face, rolling over to continue facing Kyubey. How do I have magic? How did I never know about it before, given that I have it?

It's only a little. To have more you would need to make a contract with me and become a magical girl.

A contract? What sort of contract?

Not a legal contract. You would only be agreeing to become a magical girl and fight evil witches, and in exchange you would get one wish.

"One wish?" she says aloud in surprise. "But..." Am I missing something? Or did you really just tell me I've got the power to give myself a wish? Or... wait, just to clarify, when you say a wish, do you mean, like, an any-one-thing-I-desire wish? Or something narrower than that?

I would grant the wish as part of the contract, it clarifies. You can wish for anything you like!

And what would fighting evil witches entail, exactly? Like, would I have magic for fighting them? What sort of magic do they have?

Magical girls have magic to fight witches and do other things, says Kyubey, nodding its fuzzy little head. Witches can hide themselves inside barriers so that normal people don't see them, and they have miasma that can make normal people violent or suicidal.

Shania sits up to face Kyubey more fully. Okay. So magic is good for fighting and other stuff. Witches have a bunch of stuff that works against normal people. Do magical girls not count as 'normal people' for this purpose? And, assuming they don't, what can witches do against us?

Magical girls are not normal people! Witches have deceptive shapes inside their barriers and are much stronger and faster than humans.

Okay. Sounds pretty doable. At least assuming my fighting magic is any good. Which I assume it will be? Because otherwise there wouldn't be any point in having it; I don't know how to fight at all right now, so I'm going to have to lean pretty exclusively on magic if I want to get anywhere with that. After a moment's pause, she adds, Also, about how much time will I need to spend on fighting witches? Would I be signing away all my free time if I took your contract?

How many witches you must fight depends on how much magic you want to use. If you never use it on anything else and are not inefficient in fighting them you will not need to fight a witch more often than once a week.