It’s the middle of a war, people are dying all around him, and Zabuza is excited.
A teething mission--well, it will be if he has anything to say about it, Zabuza eyes the current holder of Kubikiri Bouchou speculatively--finally, and one way or another it will be one that people will remember. He may already be infamous in the Elemental Countries already, what few civilians Kiri may have may cross the street and hide their children when he walks through the streets--even though without him most of them wouldn’t even have children anymore--but he wants to be legendary.
Escorting Kiri’s newest jinchuuriki to the sealing site is an important step to that goal, especially when there is intelligence--kami, he loves Kisame, he’d never have taken this mission if he didn’t know that--out of Konoha that they might try to interfere.
The girl is not someone he’s seen before, but that doesn’t mean much. Most people his age are either dead or far too smart to test his reputation as a comrade-killer. She’s either foreign, stupid, or both, but she latches onto him and throws a fit whenever anyone else shows up to guard her.
(He hopes she thinks she can overpower him. She’s feisty and he’d love to prove her wrong. And if she tries after the fuuinjutsu ritual? Well, Zabuza’s always wanted to fight a real jinchuuriki.)
Most of the others don’t care--though the first-caste bastard who has the sword Zabuza’s wanted his entire life turns his nose up whenever he catches sight of a third-caste orphan with such a position--and well, she might flinch whenever he starts talking about the normal stuff that Kiri kids talk about--what’s wrong with a little blood? Gotta scare the littler kids otherwise they’ll never do what you want them too--but she reciprocates pretty well with her own war stories.
Turns out she’s Konohoan, and who knew that a kunoichi dumb enough to get caught by Kiri would be anywhere near the front, let alone the faction led by the Yellow Flash, and manage to survive? Though, he has to hand it to her, she was a pretty decent medic and could throw a tantrum with enough strength and focus to make most not want to bother her, and judging medics by battle prowess was stupid anyway.
Konoha sounds nice, the way Rin talks about it, though; if a little soft. Definitely easier to grow up in than the Bloody Mist. Probably why Rin’s so soft, though, and Zabuza’d never trade for that even if monsters like the Sannin, the Red-Hot Blooded Habanero, and the Yellow Flash come from there.
Zabuza knows nothing about sealing--always better at the killing part of being a shinobi than anything else, especially when only first-caste get access to the plundered scrolls of Uzushio, and honestly likes assassination way too much to even begin to regret it--but Rin seems to recognize the array the moment she’s pushed into the concrete room.
He knows that it’s an honor to be a jinchuuriki--even if they’re treated worse than third-caste in the end--to be gifted with so much power--although you’re going to be watched carefully for the rest of your miserable life to make sure you don’t lose control. Zabuza doesn’t really get why they chose a foreign prisoner to host one of Kiri’s bijuu, but there’s gotta be some reason for it even if it’s not a particularly good one. Rin takes one look at the sealing array and tries to take his head off with a vicious kick.
She doesn’t manage it, of course, and it’s pathetically easy to knock her out, but she is the closest thing to a friend his age Zabuza has ever had, so the betrayal twinges slightly even though he’s been expecting from literally the first moment he met her. He may be a hardened killer, but he’s still only fourteen after all.
The others leave them alone after the sealing is complete--although Zabuza can feel the prickle of that bastard’s chakra somewhere close, he’s right to be wary, Zabuza’s gonna get that damn sword--and Rin slowly breathes awake. Only two of the stupid assholes died in the process--Zabuza is almost sad it wasn’t that first-caste bastard, but this way he gets to kill the arrogant fuck himself--so he guesses the entire thing was successful.
Zabuza knows when she wakes up, though, because her face shifts from uneasy but peaceful to a rictus of fear and pain that he’s more used to seeing frozen on corpses than on a living person.
“Oh, kami,” she says, and starts to cry.
Kakashi knows that Rin is close. He has to reach her. He promised.
He follows the flare of her chakra--much brighter and more potent than before, but all that much easier followed--and plows headlong into the chakra laden mist that Kirigakure is known for. It is thick enough, heavy enough, that even Obito’s gift cannot see too far into it.
Nothing to do but move forward. He can still feel Rin ahead. That--she--is all that matters. (He’ll be damned before he breaks his promise.)
The fog curls around him like something alive, warm and wet like his father’s summons--and his, but he hasn’t been able to summon them for years--after a storm, heavy with chakra and the weight of the water in the air. The mud sucks at his boots greedily, the sound halfway to sickening, and the smell of blood churned into the dirt makes him glad for his mask and the filter it provides.
It’s odd though, odd enough to set Kakashi’s nerves on edge, that despite the presence of Kirigakure’s signature technique, he faces no resistance. Only bodies, and tree roots--exposed by the sucking mud--right up until a boy who looks to be his age tries to cut him two with a massive sword almost a big as he is.
He dodges, barely--cursing that it puts him farther away from Rin’s bright beacon up ahead--and then has to quickly parry another strike with a hastily drawn and chakra reinforced kunai. The other boy is a Kiri-nin, bandages soaked in sweat and blood pooling around his neck, a vicious smile on his face. (Maybe he’s spent too long looking at bingo books, but it is strange to see a Kiri-nin with a sword and normal teeth. It makes his stomach flip weirdly, and he thinks that such a smile, in such a place, has no business looking so much like Obito’s.)
Kakashi prepares to dodge around him, prepares a chidori to go through him if necessary, but instead of attacking again the boy tips his head back and laughs wildly. He may or may not have the the prettiest neck Kakashi has ever seen, though why he immediately thinks that Kakashi has no idea, and he will never acknowledge the feeling if he has anything to say about it.
“Hey, prisoner-chan, is this your rescue attempt?” he calls, as wild as his smile, or his laugh, and Kakashi is happy when Rin--pale, shaky, and obviously terrified but so wonderfully alive--steps from the dissipating mist because he can focus on her rather than the fluttery thing his stomach does whenever he looks at the boy.
She glances at Kakashi--brown eyes full of relief and the sort of bone-deep determination that reminds him too much of Obito right before they rescued her that disastrous first time--and then she smacks the boy on the back of his head. It’s obvious he lets her, if the slight widening of his grin is any indication, and she frowns at him.
“Stop that! You know my name. And why are you so happy? Aren’t you worried?” Her arms sweep around to encompass the battlefield that is slowly being revealed and Kakashi shifts his foot from a disembodied hand while trying to ignore the easy way the boy slings the giant, bloody sword over his shoulder.
“This was my teething mission,” he says, and Kakashi is distracted when he hoists the sword again. “And I’m a known comrade-killer. Even if it wasn’t a teething mission to begin with it is now and they expect a few casualties on one.” The sword is now the brightest, clearest thing on this misty battlefield, and the boy shrugs indolently.
“A few!?” Rin screeches, and Kakashi must be poisoned or something because he could have sworn the sword had been covered in blood and cracked just a few moments before.
“I’m the Demon of the Bloody Mist,” he says, incredulously, and Kakashi knows that sword. It’s the Kubikiri Bouchou, one of Kiri’s seven legendary swords. He even knows the apparent newest member of Kiri’s seven swordsman--the picture in the bingo book of the bloody, little kid does not do him justice (apparently, reading bingo books for fun can be helpful no matter what Obi-- anyone says)--Momochi Zabuza, responsible for the murder of his entire Academy class and now, apparently, a good number of other Kiri-nin too.
Including one of the seven swordsman who’d killed Dai only the year before. Kakashi takes visceral pleasure in the knowledge that one of them died so ignominiously, even though he knows both Dai and Gai wouldn’t feel the same.
Why aren’t his teeth sharp? (He doesn’t know what it is about Zabuza that reminds him of Obito, doesn’t really want to think about it. But the wild black hair, the irrepressible grin, and the devil-may-care attitude may have something to do with it. Kakashi just would feel a lot better if Zabuza would just fit into the neat label of Kiri-nin/enemy and stop making his stomach flutter. Was there poison in the mist? There had to have been poison in the mist. Normally, he’d be good with poison, this must be pretty potent, he hopes Rin can look him over soon.)
Rin elbows him in the ribs and Kakashi pretends he was paying attention the entire time, even when she manages to knock the air out of his lungs with a hiss. “Get sensei here, Kakashi,” she says, and she sounds urgent enough to scare him. Zabuza is just watching them, apparently unconcerned that Rin is going to escape, is calling reinforcements, and is actively planning with part of said reinforcements in front of him. Kakashi pulls Minato’s tri-pronged kunai from his pouch, and he’s grateful he still has it. He cannot lose her too.
“And that’s me out,” Zabuza says, stroking the flat of the Kubikiri Bouchou possessively. “Thanks for being a part of my teething mission, prisoner-chan. I’m glad I got to kill that first-caste bastard myself.” Kakashi hears Rin grunt a little, maybe in pain, maybe in response to Zabuza, but he’s more focused on remembering how to use the Hiraishin kunai.
A brown face comes far too close too Kakashi’s, and he very nearly startles back, kept in place only by a lifetime of shinobi training. Zabuza’s grey-brown eyes are dark with glee. “I can’t wait to actually fight you, you slippery bastard. It’ll be so much fun.”
Mist fills the valley again where it had been slowly where it had been slowly dissipating, the kunai sparks with Kakashi’s chakra, Minato drops heavily into existence, and Kakashi has never been so thankful for his mask when it covers the fierce blush that rises.
Obito is found in front of the gates of Konoha a week later--missing nearly six months of memories, the strength to move half his body, and an eye but still alive--and he confesses his love to Rin the moment he wakes up.
He doesn’t get why she takes one look at Kakashi and bursts out laughing when he tells her about his crush, and he really doesn’t understand it when she chases the jounin around his hospital room with the newest bingo book open and Kakashi actually blushes and runs away. It’s not even porn inside, just open to the Kiri M-section, and Obito really doesn’t understand his friends anymore but he’s so happy he’s home.