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The first thing Kakuzu notices, the first thing that sets him off, is that Hidan doesn’t bow in greeting.
It’s a bit hypocritical; after all, Kakuzu doesn’t bow to him, either, but all the same he can’t help but feel a bit slighted. The man looks like a fucking punk, is what he’s saying, and he’s already fostering some sort of plan to get rid of him in the back of his mind.
Kakuzu hates having to work in a team. He’s only gotten this far by working alone, by relying on himself, and it’s a bit of a kick to the teeth to be assigned a partner.
But such are the rules, and beyond his customary grumbling he’ll do his best to get along.
(His best is not much at all.)
The second thing that sets him off is that past a grunt of hello, he gets little to nothing from Hidan as they set out.
He doesn’t mind quiet— it’s better than the chattering he’s killed past partners for. He does mind when the man starts to mutter to himself, just loud enough for Kakuzu to be annoyed by but not loud enough for it to be discernable.
Kakuzu peers at him. He’s fiddling with the necklace around his neck as they walk, running the chain around his fingers. His gaze doesn’t seem to be focused on anything much.
Kakuzu sighs and looks ahead. It would be a bit early to kill him.
—
His patience runs out quickly. It’s been perhaps an hour since it started, and it has not stopped. He’ll tell Pein he tried his best.
“The hell are you doing, anyway?”
Hidan’s eyes slide over to him and then away, the only sign he’s even heard him, and he doesn’t stop, and Kakuzu’s done, because people do not ignore him, and that’s final.
He stops walking. Hidan does not.
He takes a knife from his waist, and throws. It lodges itself firmly in Hidan’s turned back, making a satisfying sound.
He almost feels like it’s a waste, for just a moment, but he truly had expected the man to dodge. Pein had decided him Akatsuki material, after all. Clearly it had been a fluke. He’ll have to apologize after this for killing another teammate, but he can’t quite find it in himself to be sorry.
At least the mutterings have stopped.
And then Hidan turns around, in a way he shouldn’t be able to, because Kakuzu knows he hit his spine. His face is twisted in anger, but it’s nowhere near enough for it to be the anger of a killed man, just mere inconvenience.
“What the fuck was that?” He spits, and Kakuzu’s just glad it’s not muttering.
Well, Hidan is very, clearly not dead, and doesn’t seem to be bleeding out besides, so Kakuzu cuts his losses.
“Look at me when I’m talking to you,” is all he says.
“Motherfucker— I was busy,” he exclaims exasperatedly, as if that explains it. “At least get the knife out then, yeah?"
And maybe Kakuzu shouldn’t have doubted Pein in the first place because then he’s pulling a knife out of Hidan’s back as the man watches with something like approval and congratulates him on the throw, and Kakuzu is honestly a bit too impressed to give him shit.
Not with Hidan, no. Kakuzu is simply mortifyingly jealous of whatever this ability is.
“Explain,” he orders once the knife is out and they’ve resumed walking. He gestures at the already closed wound. When he’d pulled out the knife he could see the skin knotting closed on his back and it made his own skin crawl, but he allowed himself a few moments of watching in utter fascination before he pulled away.
“I’m immortal,” Hidan chirps like it’s the easiest thing in the world, like it’s not what he’s been lusting after his entire life, like Kakuzu wouldn’t do anything, anything to have that.
“Explain,” he demands again.
Hidan shrugs. “It’s a gift.”
When Kakuzu just stares at him he shrugs again. “From Jashin.”
Ah. Hidan’s from Yu, Kakuzu finally notices. Kakuzu doesn’t know much about Yu, but he’s heard murmurs of Jashinism before, idly remembers torturing a man for info after hearing some rumors. All he remembers is something something sacrifices and something something blood rituals. That their doctrine had something to do with immortality. And that it came from Yu.
Great. He’s been grouped with a cultist.
“I see.” Kakuzu places no great importance on religion. It’s something for people who don’t have enough to provide, who need to trust in something, who aren’t strong enough to trust themselves. It has no place with him.
“You made me mess up my prayers,” Hidan grumbles beside him, completely nonplussed, and Kakuzu groans as the muttering begins again, now completely intelligible as the rhythm of prayer.
Kakuzu finds himself hoping he isn’t truly immortal, even as he yearns to dissect it, force Hidan to tell him everything. He can only hope Hidan is at least a good fighter. Might give him a good fight on the way out.
—
Hidan is abloody fighter. That’s all he can really think after they’ve completed their first mark and Kakuzu finds himself hoping the head is at least untouched enough to be able to use to collect the offer.
And then he hears something that sounds suspiciously fleshy. He turns.
He’d noticed Hidan drawing the symbol on the ground but ignored it, but he finds it somewhat harder not to notice now that he seems to have stabbed himself through and fallen on it.
Hidan is either an idiot or really, truly immortal, and he can’t quite decide which is more annoying.
He makes his way over to the prone body and rests a hand over Hidan’s mouth. He isn’t breathing.
He really isn’t trying to make Pein’s job harder. It’s not his fault he continues to get paired with idiots. At least he hasn’t killed this one, even if he isn’t quite sure Pein will believe that Hidan killed himself.
He sighs and goes about finding the head he needs for the reward. When he’s done he leans over Hidan one final time, careful not to step inside the symbol on the floor— he may not believe in anything, but that doesn’t mean he wants to risk it— and peers at him.
He truly isn’t moving. Oh well.
And then he does, eyes jumping open and a breath heaving from his mouth. Kakuzu very much does not jump.
“You’re alive?” He asks as he steps back, watching Hidan gasp and cough. Blood shoots from his mouth and he rolls onto his side to hack his guts up the best he can with a fucking scythe in his chest.
“Yeah, yeah, fine,” the man who very much does not look fine but has already surprised him groans, and Kakuzu shrugs.
He watches in sick fascination as Hidan pulls himself together, mutters another short prayer, and yanks the scythe out without so much as a second thought. He gets to his feet even as blood gushes from the open wounds, though Kakuzu can once again see as it slowly starts to close.
“What the fuck,” he mutters to himself, shaking his head. He calls out, “I’m leaving.”
“Give me a fucking minute here!” Somewhere in the midst of the battle Hidan had put aside his Akatsuki robe and now Kakuzu watches as he sorts through the dead bodies to find it.
And then Hidan is at his side again, and he can see that the scythe wounds are already healed, only a few pale lines to show they were ever there. Even those fade.
—
Having had to forgo his immediate plans to kill him, Kakuzu sets about to learn absolutely everything he can about Hidan’s immortality instead.
Instead he finds himself learning altogether too much about Hidan himself. This, of course and in no small part, involves learning far too much about Jashinism.
Hidan believes that a deity has blessed him with his immortality. Kakuzu does not. Kakuzu had lived long enough to know that chakra does crazy things, and he has lived long enough to outgrow any juvenile belief in something greater.
(He tells this to Hidan, of course, and is quickly threatened with claims of heresy. He tells him this is not how it works. He also cuts out as much of his tongue as he can manage when Hidan doesn’t shut up. It isn’t worth either how long it takes to reattach it or the whining that follows.)
Hidan believes it’s his sacred duty to kill. Kakuzu believes he’s genuinely flat fucking crazy, tells him as such, and believes he’s just looking for an excuse.
Kakuzu is really starting to wish he could kill him, potential conquest of immortality be damned.
—
Kakuzu does not start to care about him, and this is why he’s not concerned when a ritual goes wrong.
Hidan has complained all day. Complained that he’s tired. Complained that Jashin is louder than normal, whatever the fuck that means. Complained, of all things, that can’t they leave the mark for tomorrow in an uncharacteristic laziness and an even more uncharacteristic lack of calls for bloodshed.
So sue him, he was keeping an eye on him. Hidan has survived long enough for him to not want to recommit himself to a new partner. It would be a lot of trouble. That’s all.
Hidan spears himself through as is usual, and Kakuzu tells himself stubbornly there’s nothing to worry about, pulls out his bingo book to occupy himself.
And then Hidan doesn’t get up.
Some rituals take longer than others, he’s learned entirely against his will. Sometimes it’s five minutes, other times an hour or two. Both are a waste of time.
He doesn’t quite care until it’s been four hours and then he’s more annoyed than anything.
There’s nothing he can do to speed it along, nothing he can snap to a dead body, and it’s frustrating.
And, he finds, when he’s growing slightly… concerned… even moreso.
There’s nothing he can do but wait. He wonders idly to himself how long he will. How long he’ll sit here like a fool until he gives up and admits the immortal man is not immortal. Wonders if he’ll be content that his jealousy, his belief that immortality isn’t real and never has been will feel satisfied.
But perhaps he’s become senile because he’s grown accustomed to having someone around he can’t kill. Someone he doesn’t need to worry about, someone who understands what it means to be immutably and inherently violent.
No. He kneels over the body, doesn’t dare step inside the symbol in something as close he can come to respect, and hopes, for once, that Jashin is real.
—
Ten hours.
Ten hours and Hidan groans, rolls over onto his side as he always does, and coughs up some blood.
Kakuzu pulls back, refuses to be gentle because he never has been and won’t be now, and snaps, “The fuck was that?”
“What?” Hidan murmurs blearily. There’s still something wrong. He’s not supposed to be out of it. He’s supposed to hop up and snap at Kakuzu and complain about blood on his robes.
“Get up, idiot.” He’s very careful to keep any emotion out of his voice.
“Fuck, fine, just give me a fucking minute here.” He blinks up at Kakuzu. He frowns. “Why’s it dark out?”
Kakuzu scoffs. “Fuck off.”
And Hidan grins and holds up a hand for Kakuzu to pull him up. And Kakuzu rolls his eyes and complains and pulls him up anyway and feels his pulse in his wrist and is maybe a little bit glad.
Maybe.