Based on a Les Mis kink meme prompt:

Cosette as a magical filly

that's it that's the prompt

This is also my first fanfic ever, so I have basically no idea what I'm doing. I own nothing, etc.

A pink-haired girl is cringing on her bed. The girl seems to embody the tragic picture of one far too young who is shouldering far too much grief. She clutches her head in her hands, trying in vain to block out the painful images. Tears of pain, anger, and grief leak from her eyes. The deceptively innocent figure nestled within her childhood toys seems to stare into her soul.

You can't believe that? Then shall I show it to you? Shall I show you the history spent together by mankind and Incubators?

In a town called Montfermeil, there lived a little girl who was called "Cosette" by her mother, "that horrid girl" by her caretaker, and "the Lark" by everyone else. On one particular day this little girl, with a black eye and wooden shoes and hair matted with dirt, was carrying a bucket far too heavy for her through the woods when she came across a cat.

"Hello, M'sieur Chat."

"I'm not a cat," said the cat.

And indeed, it wasn't. The not-cat had strange appendages coming out of its ears, wide, unblinking pink eyes, and a red oval on its white back. "My name is Kyuubey. And you're Euphrasie."

"Oh!" said Cosette, for Euphrasie was indeed her Christian name. "How did you know that?"

"I've been looking for you. I want you to make a contract with me and become a magical girl!"

At this, Cosette seemed to shrink into herself, for if someone was looking for her, it usually meant she was about to be beaten. As she ran back toward the village as fast as she could with the heavy bucket, Kyuubey stared after her with unblinking eyes.

The next time the local priest invited Cosette into the church for some bread, she was able to indulge the curiosity she usually kept so carefully hidden.

"Monseigneur, what is a contract?"

"Why do you want to know, my child?"

Cosette seemed to shrink into her chair and look away evasively.

The priest was a kindly man and knew all too well just what went on in the Thenardier household. The best he could do was give the Lark a place to rest for a bit and eat a piece of warm bread. He had learned when not to ask too many questions of the little Lark, for fear of her retreating into her shell. Yet her question-and when was the last time she had felt confident enough to ask a question?- was so odd that he had to ask. Seeing the child retreat into herself, though, he could kick himself, Instead of that anatomical impossibility, he resigned himself to answering the child's question, though it seemed to be almost darkly ominous.

"A contract is a legal agreement between two people, where one person agrees to do something for the other in exchange for some sort of payment.

Large eyes blinked in a too-thin face. "Does it have to be between two people?"

"Ah… yes child. It is between two human beings."

"Oh… merci, Monseigneur."

The next time the young Lark was in the woods, the creature appeared perched on a gnarled tree branch above her head.

"Hello, M'sieur Chat," said Cosette, who had quite forgotten her earlier fear.

"Hello, Euphrasie," said Kyuubey—who was still not a cat.

"The priest said that contracts can only be made between two people, and you are not a person," said Cosette.

Kyuubey's tail twitched. "It's a special contract. You become a magical girl, and fight witches, and in exchange I give you one wish."

Now the young girl's curiosity—beaten into submission after asking too many questions of an irritated and violent innkeeper's wife—was piqued. "What's a magical girl? Are the witches like the ones in Eponine's storybook? Will you really give me anything I wish for?"

"A witch is a creature who spreads fear and despair, just as magical girls spread hope. If you become one of these warriors of hope, I can grant any miracle you can think of."

This shocked the poor girl into silence, for when you have nothing, what can you possibly say when you are offered everything?

"I…"-quietly, so quietly—"I wish my mama would see me again."

"Euphrasie—you are now a magical girl. Embrace your destiny!" said Kyuubey. And then he plunged his long ears into her chest.