Disclaimer: I don't own Naruto.
It started the night they met. Zabuza had, before learning her name, addressed her as "boy", being under the erroneous impression that she was one.
Haku hadn't had the opportunity to wash of find clean clothes yet. She was filthy, it was very dark that night, and since her ragged clothing didn't really indicate gender either way, Haku assumed that Zabuza must have been going on her voice, which was admittedly deep for a girl her age, to determine if she was male or female.
It took Haku a few hours to work up the courage to quietly correct him and tell Zabuza that her name was Haku, and she was sure he had heard her, but Zabuza continued to call her "boy".
Haku didn't bother correcting him the second time he called her that.
.x.X.x.
The open road really was no place for any child, let alone a young girl, to be travelling.
A few months after they met, while they were walking along a mountain road, Haku tripped over a rock and fell, skinning her knee in the process. She sat there, stunned for a moment, then started to cry.
Zabuza learned down beside her, paused, then slapped her across the face. It wasn't a harsh slap to hurt her and make her feel even worse, but a sharp slap to snap her out of it and get her attention.
"Get over it," he told her bluntly. "It's just a scratch. A shinobi does not cry over pain."
They continued walking, and within a few minutes Haku couldn't feel the scratch anymore.
And there were more serious dangers facing a female on the road.
At one point in their travels, Zabuza and Haku were waylaid by a pair of men intent on robbing them. Zabuza had a scheme going to turn the tables on the aspiring robbers and scrounge up all of their money.
One of the men was looking at Haku in a way that was making her extremely nervous. His eyes had an odd hunger to them, malevolent and greedy.
Zabuza noticed, and scrapped his elaborate plan by using Kubikiri Hōchō to cleanly decapitate both of the robbers in one swift stroke.
After denuding both of the headless corpses of money, foodstuffs, weapons, and what clothing that could be salvaged and used, Haku found herself on the receiving end of an awkward talk about sex was, delivered by a supremely embarrassed Zabuza, who didn't want to be telling her this in the first place, but knew he had to, and was thanking his lucky stars that he had grown up in an all-female household. He also told her that if she ever caught a man looking at her like that again, she shouldn't hesitate in goring the man with either a spike of ice or senbon needles, depending on what she was feeling more savvy about at the moment and whether or not she wanted to kill him or just leave him a few scars to remember her by.
Haku gaped at him for a few moments before recovering her composure. She didn't say a single word for the rest of the day, and for the first time in her life Haku wished she wasn't female.
.x.X.x.
The shinobi world was hardly any better a place for a woman, as it happened.
Kunoichi's services at bed and board were bought and sold like cattle at a fair. Their abilities were demeaned and devalued in Kiri, kunoichi there being seen as inferior to men and treated as such. In Kiri, the sole difference between a kunoichi from a lower class family and a prostitute was that for the most part, prostitutes didn't kill their clients or run off with all their secrets.
A brutal example of this came down to Haku through Zabuza's tale of his older sister Mayuri. Mayuri had been pregnant at least four times by the time she was nineteen, aborted two of those pregnancies, had one miscarriage that Zabuza knew of (though he was almost certain there had been more), and eventually died of a disease she had contracted from a businessman she had been sent to seduce. At her point of death, nearly all of Momochi Mayuri's thick brown hair had fallen out and her body was an emaciated, feeble wasteland. In the interest of the child, Zabuza had allowed a couple he knew who could who had no children adopt his nephew.
Part of the reason behind Zabuza's failed attempt upon the Yondaime Mizukage's life had been the order that had brought his sister low.
Kunoichi were cannon food destroyed a thousand times in a world of expendable soldiers.
Of course, it slipped Zabuza's mind to tell Haku that Yagura's successor was a stunningly attractive young woman, who, like Haku, had suffered during the purges due to her birth into a kekkei genkai clan (she had in fact two bloodline limits), but unlike Haku reveled in her femininity and had issued reforms limiting the number of seduction missions a kunoichi could be sent on within a period of five years, raised the minimum age required for seduction missions from thirteen to sixteen, offering aid to unwed mothers in the shinobi world and offering medical coverage to all shinobi suffering from venereal disease.
Haku also recalled the story her mother had told her in secrecy the day she had unlocked her sleeping bloodline. During the Kiri purges, Haku's mother, separated from most of her family and unsure if any of them were still alive, sought the protection of a powerful councilor by becoming his mistress. She managed to live in stability for two years, and even bore her lover a child, a much-older brother Haku had never met and was fairly sure was dead. However, after the councilor had tired of her and she no longer served his purposes, he cast Haku's mother to the four winds and to the mercy of a prejudiced and frightened country.
Seyuki looked at her daughter and said, "When you get older, if you ever take a lover, never trust him to keep you safe."
And Haku would never forget her mother's ultimate fate.
.x.X.x.
It was, Haku decided, disadvantageous to be a woman, in every way.
She would never be considered the equal of men on the battlefield, nor would she be particularly well-adapted to life on the open road. Zabuza never voiced those concerns, but they were always there, and Haku felt them keenly.
There was a wall there. Haku felt trapped. She didn't particularly want to be a man, but being a woman wasn't doing her any favors. In order to become stronger, to become someone truly worthy of being valued, Haku needed to become something else.
So she became a he.
.x.X.x.
Haku had always preferred wearing boy's clothing. They were more comfortable, warmer in cold weather, and far easier to walk in for long periods of time. Haku disliked the clinging, tangling skirts of girls' kimonos and the way she tripped over them whenever she wore them.
She adopted more the manner of a boy. She was still her quiet, polite, demure self, but she became more energetic, more inclined towards running off after animals in the forest, particularly rabbits, and devoted far more of her time to training to control her kekkei genkai. Haku allowed cuts and bruises and scrapes and scars to accumulate across her arms and legs; while not conspicuous, they made her feel better.
It helped that Zabuza had always treated Haku the way he would a boy. Subconsciously, Haku wondered if he had done that in anticipation of the transformation Haku would undergo later.
Unfortunately for Haku, her body started to change in ways that were a bit hard to ignore. Almost impossible, actually. "You're too pretty for anyone to mistake you for a boy," Zabuza pointed out. Haku didn't listen.
She bound her breasts (not that there was much there to bind in the first place) flat against her narrow chest and began wearing baggy clothes that effectively hid tiny curves and the differences between a man and a woman's ways of walking. She chewed on a sharp-smelling, foul-tasting root that happened to grow in abundance in Nami no Kuni to stop menstruation, and when Zabuza eventually started to complain of the smell (he had his limits), Haku burned incense and chose to smell of that instead. Her one concession to femininity was her long black hair, falling slightly past the middle of her back.
There were a few things she didn't want to change about herself. Haku would alter her personality only slightly, and in the end she assumed a manner that was neither especially feminine nor particularly masculine. That, combined with her noticeable lack of height and the fact that her face matched almost exactly the proportions of a china doll tended to make people think that she was a woman, but her choice of clothing (what self-respecting teenage girl wore the clothes Haku did?) and that she answered to "boy" generally convinced them that she was one.
.x.X.x.
The transformation was complete. Everyone around her but Zabuza was convinced that she was a boy despite her feminine appearance, and Haku was content.
She never felt any special inclination to be a boy, but she knew that in order to be respected, in order to be even remotely safe, she needed to become one. And Haku was a consummate actress; she could assume any role needed or wanted when she went on to the stage, as the situation demanded.
It was an odd feeling though. Haku was female and had never thought "like a man" in her life, at least not as far as she knew. Haku knew deep down that she was a woman even if she rarely acknowledged it anymore, and claiming otherwise was a bit like wearing a mask that didn't quite fit right.
She felt…out of place.