I use a lot of Japanese words in this story. Some translations are:

Bijuu: Tailed beasts

Kitsune: Fox

Kyuubi: Nine-tails

Machigai: Mistake

Tanuki: Japanese raccoon

Yokai: Spirits, non-humans

Ichi, ni, san, shi/yon, go, roku, shichi, hachi, ku/kyuu: One through nine


Once, a powerful demon attacked the village of Konoha. It was the great Kyuubi, a nine-tailed fox, powerful beyond the villagers' wildest imaginings. It struck with a devastating force that would have demolished the village, but for one man. Yondaime Hokage, Namikaze Minato, sacrificed his life to seal the beast inside his infant son, who had been born that day to Uzumaki Kushina, a beautiful woman with red hair…
There was once a great demon-god lord, a powerful ruler of the yokai, who wished to extend his rule to the human world. So he decided that he would have eight daughters, one for each point of the compass, and that they would serve under him so that he might rule the world of the spirits still, while having delegates in the world of humans.

He set about finding mothers to bear his children. He could not use yokai, because his daughters must have a connection to both the human and spirit worlds, but he could not use humans, because the human half would rebel against his commands. So he decided to father children with eight animals, whose spirits could easily be dominated by their yokai half, but who could live in the human world. He lay with a tanuki, a cat, a turtle, a dog, an eagle, a serpent, a wolf, and a tiger. His work was done, but before he could return to the spirit world, he encountered a beautiful kitsune. She spoke to him, inviting him to come drink saké with her. Once she had gotten him drunk, she seduced him, and he lay with her. He woke later with no memory of these events, and returned to the world of the spirits convinced that all had gone as planned.

Demons grow fast within their mother's wombs, so he returned in one month to claim his daughters. He gathered them to him, but as he went to take them, a she-kitsune came forward. In her mouth she held a kit with glossy red fur and nine tiny tails.

"This, too, is your daughter," she said, and gave the kit to him. Holding it in his hand, he could tell that it was stronger than its sisters. Its power intrigued him, so he took it with him, though he had not planned it.

He took his nine daughters, the bijuu, to a home he had prepared for them, a giant cavern at the bottom of a whirlpool. And there he raised them, for hundreds of years…

Ku

I was the youngest of my sisters, and the strongest, and the worst behaved. Because of my kitsune form, I had shape-changing abilities, and I abused them terribly. I loved nothing better than to take the form of a local god and go terrorize nearby villagers. Or maybe I would become a frog, and go converse with the other frogs at the bottom of the lake, or perhaps a falcon, and soar the skies. But there was one form that intrigued me most of all.

When I first began to take on human form, I had no idea of its subtleties, having no human in me. I would merely imitate the exact form of a human from a nearby village. It always delighted me to see them run in terror from what they assumed to be an evil doppelganger. But gradually, over time, over a span of centuries, I began to understand the human shape, the small variances that differentiated them. I began to create my own forms, taking elements from various humans. Finally, I settled on one shape; a young female human with deep blue eyes and hair the same tawny red as my fox fur. This shape felt right somehow, as if it was the form I would have been born with had I been born human.

But of course, this shape could never feel as right as my natural form, my true form, that of a nine-tailed demon fox. In this form, I was pure raw emotion. If I was angry, I might raze a village or crush a mountain range to pebbles. If I was restless, I might wear a valley in the earth with my pacing. If the slightest thing saddened me, I might weep a lake of salty tears. Unlike humans, I did not simply feel my emotions, I was them. This was what I truly was.

Father and my sisters disapproved of my shape-changing into a human. They thought that I might become one eventually. I merely scoffed, laughed at them. They simply didn't understand the powers of the kitsune. Only my eldest sister, a tanuki demon, could begin to understand, but she much preferred her true form and seldom changed shape. Of course, I was stronger—much, much stronger than her, so it might be that she would not be able to retain herself if she took human form too frequently. But I could. Of that, I was sure.

When I was young, only a few hundred years old, Father brought a woman to our home, our underwater cavern. To the others, she was simply a human creature, but after my years of study of humans, I could tell that she was a tall and slender female, with long, dark hair, and soft white eyes that were glazed and vacant. I asked Father about her, and he told me that she was of a prominent human clan, that she was under his enchantment, and that she was pregnant with his child.

"Why?" I asked. "You already have nine daughters to rule the earth for you. Why would you need a human child, too?"

"You are to rule," he replied, "but I wish also to create a legacy, a clan of humans to rule under you, lords of men."

A month later, the woman cried out, and her eyes widened even as they gazed blankly ahead. Father was not there, and my sisters showed no interest in her, so, taking my human form, I knelt beside her and took her hand. I peered down into her anguished face, not with human emotions, not with pity or comfort, but with a fierce curiosity. Using the sleeve of her kimono, I wiped the sheen of sweat from her face. I knelt beside her and held her hand, and she gave birth to two half-human infants, a male and a female. I turned to show them to their mother, and she blinked, once, twice, in surprise, then her eyes half-closed and her raised hand fell limply to her side.

Moments later, Father came down the whirlpool. Noticing the twins, he flew to my side.

"Ah," he said. "The human has given birth."

"She's dead," I said, but he didn't appear to hear me. He picked up the male baby and looked into its face. It had black hair like its mother, and glowing red eyes. "Madara," Father murmured. "Your name will be Uchiha Madara, and I will make a great nation of you. Your chakra is strong…"

"Father," I said, "what of the female?"

"She has too much human in her. She is useless, she is nothing. Her name will be Machigai—she is nothing but my mistake. I had not counted on twins."

"What shall we do with her?"

"You can have her," he said dismissively. "Kill her, abandon her, raise her, whatever you wish."

"I will raise her."

He eyed me scrutinisingly. "Sometimes I think that you have too much human in you as well, Ku." He took the male—Madara—and turned. "Now I will take this one to his grandfather. Farewell, my daughters."

I stood angrily at the entrance to our cavern home, glaring after him. There was no human in me, none at all! My mother was a kitsune and my father was a demon.

So how could I be human?

The female infant let out a soft wail and I went over and picked her up. Looking down at her, I saw that her hair and eyes were a soft dove grey. She cried again and moved her head from side to side, searching for food. I loosened the neck of my kimono and lifted her to my breast, willing milk to flow. It did, and she made contented baby noises as she drank eagerly.

Shi, my dog demon sister, padded over to me and lay down, the tips of her ears level with the top of my head when I knelt and she rested her head upon her paws. Her size did not intimidate me; I am much larger in my kitsune form.

"Giving suck to a human brat, Ku? Soon you'll be bearing sons for some nobleman."

I glared at her, all my fox ferocity in my blue human eyes. "So Father is allowed to build a human legacy, but I am not?"

Shi sneered. "So you're planning on building a legacy off that brat, Ku? Give it up. You heard Father. She's too weak, too human." She rose, and turned, but threw one last taunt over her shoulder. "Sort of like you."

Dropping Machigai, I leapt at Shi, changing to a kitsune in midair. I slammed into her, pinning her to the stone floor. Raising my claws, I slashed four cuts across her muzzle.

"That was a warning," I growled. "Insult me again, and I'll kill you!" I lifted my paw, letting her free, and she darted away with her tails between her legs.

Smiling, I returned to human form and went to pick Machigai up, and, stroking her hair to calm her, I resumed nursing.