Chapter Text
The first time Kokushibo sees Kamado Tanjuro, it's New Year's Eve.
He wanders the woods of Mt. Kumotori on a whim, following rumors of a man with red hair, red eyes, and hanafuda earrings. The Tsugikuni family holds no exclusivity on red hair and eyes, but those features paired with the earrings…
Yoriichi, to his knowledge, had no descendants. But Kokushibo had stood over the pieces of his brother, waded through the blood and bone to pick out the remnants of the flute he'd kept on his person even decades after their separation. He hadn't seen any earrings.
Reasonably, this family could be his descendants instead. He wouldn't put it past his younger twin to have been sentimental enough to leave the earrings with his in-laws, or his niece or nephew (whichever, Kokushibo has forgotten what child he'd had). But, far more likely, this has more to do with his brother than him.
So he climbs the mountain, trudges up the steep path and the calf-deep snow. Before he even reaches the top, he smells fire, feels warmth on his skin.
Then, he catches the blaze of something red, and orange, and bright. It curves, bends, strikes. As if someone has taken sunlight and shaped it to their will.
Kokushibo has only been afraid of two things—the first, death, he'd circumvented by pledging allegiance to Muzan and trading his humanity for conditional immortality; the second, Yoriichi…his passing had been the one thing death had been good for. Even then, his brother was something Kokushibo couldn't overcome, someone he had to outlive. Death had to claim that blessed wretch before he was fit to stand over the man's torn body.
It's instinctual for him to freeze in his tracks, stare at the flames left behind by what is surely a sword, slashing and cutting into the familiar forms of his brother's should-be-extinct breathing style. It's less instinctual for his fear to double and resonate as Lord Muzan’s cells echo it; less instinctual to cower at the thought of an old enemy coming back from the dead. Kokushibo, at the very end, had at least faced his brother with his sword drawn. He had not been the one to turn tail and run.
But that besides, this can’t be. This is impossible. If Yoriichi was meant to be reincarnated, why wait for so long? Why only now? Why not bring him back when Muzan was at his weakest, still recovering from wounds that burned even years after they were dealt to him?
This must be something else, something explainable by more ordinary means.
Kokushibo forces his feet forward and presses on.
He's met with the face of his brother.
Young, so much younger than the last time Kokushibo had seen him. His cheeks are soft with youth, his eyes shine bright underneath the shroud on his head. His hair isn’t as long as it had been when he’d died, but still long enough to tie up. On the left side of his forehead sits a mark—a scar.
Not a birthmark. No red flames snake over his temple and up his face.
It’s that detail that snaps Kokushibo out of his stupor. That dreadful little mark that had once branded his brother special and the rest of the corps inadequate has been replaced by an ugly, discolored patch of flesh. It’s certainly big enough to hide a birthmark if the thing had been burned off the young man’s skin, but there’s enough plausible deniability for Kokushibo to dismiss the thought.
It’s just a scar; this is not Yoriichi. Just a ghost with his face and his breathing style.
“Sir?”
All six of Kokushibo’s eyes snap to the young man’s direction. He’s stopped performing, ceremonial sword at his side as he lifts the shroud he’s wearing from his face. Another thing that furthers Kokushibo’s denial—the young man wields a ceremonial sword and wears ceremonial robes. No corps uniform, no nichirin blade; this young man is not a demon slayer. Had Yoriichi cursed this world once again, he would have been out there slaying demons and hunting down Muzan; his exile from the corps hadn’t been enough to stop him, after all.
“Do I know you, sir?” the young man continues. The expression on his face is placid and calm, but he squares his shoulders and braces his feet. Kokushibo watches, through the Transparent World, as his lungs expand, his muscles tense, and the synapses in his brain fire.
Curiously, he has no battle presence. Barely any kind of presence at all, really. All living creatures have a presence, with some species—namely, demons and humans—having more than others, but this young man blends seamlessly with the trees and the snow around them. Had Kokushibo not been looking at him, he wouldn’t even notice he was there; he hadn’t, earlier, until he’d seen the flames from the young man’s swordwork.
This is not Yoriichi. But.
He’s something. Not a descendant of Kokushibo’s, his blood would have been able to sense that, but something undeniably tied to his brother. He has to be, to inherit Yoriichi’s earrings, his face, his abilities—his technique. That unfairly blessed technique that no one, not even accomplished swordsmen from the golden age of demon slayers, could learn or replicate.
“What is your name, boy?” Kokushibo asks.
The young man just stares, still with that uncannily familiar tranquility on his face. His eyes scan Kokushibo slowly, with his gaze lingering on the scabbard by the demon’s hip.
“Kamado Tanjuro, sir,” he answers eventually.
Kamado. Not Tsugikuni.
Not that it should matter. Kamado isn’t a corps member, but he clearly knows enough. He’s a liability, a stain that should have been wiped out four hundred years ago, a Sun Breather.
Kokushibo reaches for his sword and strikes.
His blade clashes with Kamado’s ceremonial one, metal scraping against wood that effortlessly redirects his attack instead of meeting it head on. The deflection forces him to angle his blade away, while the force of his blow forces Kamado backward.
All the while, the man’s battle spirit doesn’t rise. Even as he takes a step back to steady his stance and readjusts the grip on his weapon, the calmness of his expression doesn’t so much as twitch.
“Where did you learn that breathing style?” Kokushibo asks.
Kamado takes another long pause to answer. “It’s been passed down in my family for generations.”
The world tilts.
Yoriichi passed on a legacy.
Somehow, somewhen, he was able to find a successor to inherit not only the earrings their mother made for him, but his sword style. He's lived on, in the background, for four hundred years. He has a legacy.
Of course he does. Why is Kokushibo even surprised? It’s his favored younger brother, who must always have everything he doesn’t, do everything he can’t. Even when his breathing style was so difficult it couldn’t be learned without his students’ bodies giving out, he still found a way to pass it on.
Kokushibo inhales deeply and readies himself for another attack, this time a proper breath technique—
But sunlight crests the hill at that exact moment. Rays of amber light pierce the fresh snow around his feet, narrowly missing him. He backs up; in his periphery, he spots a tiny house just a few meters away, and realizes the only reason the sun hasn’t burnt him to ash is because he’s standing in its shadow.
Kamado, across from him, stands bathed in sunlight.
Kokushibo sheathes his sword. This would be a foolish and needlessly reckless battle, there’s nothing for him to gain here. He will slay Kamado when the sun sets.
He spends the day mulling over the how's and why's of Kamado's existence.
While Lord Muzan had hidden himself to recover after his disastrous encounter with Yoriichi, Kokushibo had kept an ear out for his brother's business. He'd never seen him, never crossed paths with him before he felt ready, but he'd paid attention to the whelp's comings and goings as best as he could from a distance. Most of it was monotonously the same: he'd be spotted someplace, slay whatever demon had the misfortune to be in his vicinity, then leave.
No news of whatever connections Muzan could leverage. No civilian weaknesses.
Clearly, they've missed something.
It's for this curiosity he doesn't rend Kamado limb from limb when he meets him again that night. Instead of his ceremonial sword, the young man stands with an axe in hand; despite the image of being prepared for a fight, his battle presence is as nonexistent as it had been yesterday.
Kokushibo eyes the meager weapon. Surely, the boy doesn't expect to fight him with that.
“I am no swordsman, sir,” Kamado says unprompted—he must have gleaned Kokushibo's skepticism from his prolonged glance. “I come from a family of charcoal makers.”
“Then how has Sun Breathing been passed down your family?” The middle pair of Kokushibo's eyes snap up to the young man's face.
Like yesterday, Kamado takes another long while to answer. “I’ve known it as the Hinokami Kagura my whole life.”
Hm.
Interesting. At some point of Sun Breathing's preservation, either the origins of the technique were muddied by imagination or someone deliberately altered its history to protect its successors from the fate Muzan decreed for all Sun Breathers.
“And your father and his father before him?” Kokushibo asks; clarifies.
“To my knowledge, they knew it as that as well.”
So wherever this title change happened, it wasn't recent.
“Does the name…” Kokushibo pauses, almost stops speaking altogether to just skip to the battle, but this oddity will gnaw at him if he doesn't inspect it. Moreover, this is a flaw in the measures he and Muzan have taken to squash what remains of Yoriichi. It would be foolish to leave this blind spot unaddressed. He presses on. “Does the name Tsugikuni Yoriichi hold any significance to you?”
Kamado's brows slope ever so slightly. After a long, long while, he shakes his head. “No.”
Hm. Either Yoriichi was never part of this bloodline—which Kokushibo doubts given the uncanny resemblance—or his name was struck off record to protect the rest of the family.
No matter. He's done his due diligence and Kamado has outlived his usefulness. Kokushibo would simply have to bring this information back to Muzan, and have the Kamados, and all branches of the family, wiped off the earth.
He draws his sword. Kamado readies his axe.
Infuriatingly, the young man is capable even with an insufficient weapon.
He darts in and out of Kokushibo's range like a whipcord, parrying blows and dealing fast strikes that would have easily cut through the demon's skin had the axe been nichirin. It isn't, so while Kokushibo feels its pressure, it deals no damage outside of ruining his kimono.
A fact that Kamado should be aware of, but the young man doesn't seem bothered by it—then again, he doesn't seem bothered by anything. He just dodges, weaves, and returns the violence thricefold.
It takes a few minutes for Kokushibo to realize he's not fighting to kill.
Kamado glides across the snow to bat away Kokushibo's Blood Demon Art crescents and strikes, but he never aims for the neck. It would be futile to, of course, but the calculation in his eyes and movements betray something above resignation. Kokushibo’s gaze flickers to the house meters above them, at the top of the mountain.
This man isn't fighting an already lost fight—he’s protecting the house from Kokushibo. It's empty; Kokushibo can't sense anyone in there, but Kamado appears determined to shield it until sunrise.
It's almost impressive, if it wasn't so foolish. Surely, the young man doesn't expect to come out of this endeavor successful; perhaps his hubris stems from never having encountered a Waxing Moon before. Perhaps he doesn't understand who Kokushibo is.
He will learn, then.
“Moon Breathing, Sixth Form: Perpetual Night, Lonely Moon – Incessant.”
A flurry of crescent moon surges toward Kamado in a wave. The young man readjusts his grip on his weapon, and his breath mists as he inhales.
In the darkness of the night, the axe blade lights up red.
Kamado is not a swordsman.
Beyond his words, that much is obvious from how he holds his weapon, how his back moves when he swings. He is a charcoal maker, whose talents lie with the axe and the kiln and nowhere near combat.
So why is his axe buried halfway through Kokushibo's neck?
The heat of it is muted and jagged, like a dull blade forced through flesh with blunt force. It holds none of the sun's warm wrath, but Kamado holds it tightly enough that his body temperature has seeped into the weapon. The wooden handle of the axe smokes in the cold weather. The axehead glows bright.
Had it been nichirin—Kokushibo bares his teeth.
“My brother has something to do with your family,” he hisses, broken sword in a white-knuckled grip. Kamado's Sun Breathing had shattered it and its regeneration has slowed. “I know it.”
“I've never seen the name Tsugikuni Yoriichi in our family records, sir,” Kamado says, infuriatingly calm even as he tries his best to drive the axe through Kokushibo's neck.
With a grunt, Kokushibo manifests red blades to spike through his body. Kamado hops away.
Taking advantage of the reprieve the distance gives him, Kokushibo concentrates, wills his half detached throat to heal. It doesn't. Damn it.
“May I ask why you think that, sir?” Kamado continues as he braces one foot behind him in preparation for another breathing form. “Admittedly, I don't know much about the Hinokami Kagura outside of it being a dance in our family.”
Fool. Of all the people to inherit something as valuable as Sun Breathing, it had to be this ignorant simpleton who knew nothing about its history. Bad enough he was bastardizing it by fighting with an axe; he used it without knowing the full breadth of its significance.
It was demeaning. Infuriating. Insulting to—
Sunlight over the mountain again. Kokushibo slinks into the darkness.
He hides his injuries.
He hadn't lost, per se, but to be struck by a non-slayer with an ordinary axe— Kokushibo has endured enough humiliation from Yoriichi in his life. His death echo will not embarrass him further.
Muzan is as furious as he always is when news of a new Sun Breather is found, but his ire calms when Kokushibo tells him that Kamado is a mere charcoal seller. Nakime only has a handful of rooms in the Infinity Castle to repair.
He sends the Waning Moons to the mountain to take care of it, and returns to searching for the Blue Spider Lily.
None of the Waning Moons return. Kokushibo takes a year to fully recover from his wounds.
He returns on New Year's Eve once the burning in his scars gets bearable. The entirety of the Waning Moon roster has been replaced, but Kamado has not done anything of note and has remained on his mountain, so Muzan has not allocated any more resources to eradicating him than he has to. The Blue Spider Lily is his most important goal; it appears, in his eyes, that it would be a waste to send a Waxing Moon to squash one bug minding its own business.
Kokushibo has his thoughts but Muzan is his Lord. Insubordination does nothing to serve hierarchy and only causes destabilization.
So he keeps his opinions to himself and searches for Kamado himself instead. The boy is dancing when he gets there, once more with his ceremonial sword and robes. He doesn't stop even as Kokushibo halts by the edge of the woods, though he must notice, what with how sharp his senses are.
His movements are sharper this time around, tighter and less wasteful. In the year since Kokushibo has seen him, he's improved remarkably; he puts his back into his swings and conserves energy by performing only the necessary movements of a breathing form. He was already plenty capable before, but he's somehow gotten better.
Perhaps sending the entirety of the Waning Moons for him to pick off was not the best course of action.
But it's mesmerizing. He twists and turns in his robes, rendered red and gold by the firelight, and for a moment, Kokushibo is four hundred years in the past, watching his brother demonstrate his breathing style.
Yoriichi's haori floats in the wind with every graceful pivot and leap. His sword leaves glowing trails with every slash and arc. He turns and looks to Michikatsu with his wide, empty eyes as if waiting for him to say something, anything, but Michikatsu doesn't understand what he wants. He never does.
(“I will think about this flute as if it were you, Brother.”)
Kamado finishes the kagura at daybreak, barely out of breath. He lifts his shroud and turns to Kokushibo, with the same flat expression on his face from last year.
His hair is longer now.
“Sir,” Kamado greets. “Thank you for letting me complete the kagura.”
He didn't, but he can't say he'd spent hours stuck in nostalgia. Especially not when Kamado looks at him with his little brother's eyes.
“I looked into our family's records,” Kamado continues. “But they only go as far as the Sengoku era, I still couldn't find your brother.”
There's some irony to the greatest breathing style in existence falling into the hands of its progenitor's spitting image, only for that successor to know nothing about the man whose face he wears. It's disrespectful to Yoriichi's memory. It's tragic, in a way that leaves a bad taste in Michikatsu's mouth.
“He created what you call the Hinokami Kagura,” Kokushibo says. “He wore those earrings you wear now. Our mother made them for him.”
“Oh.” Surprise flits across Kamado's face, the most vivid emotion Kokushibo has seen on him. He reaches up to pinch one earring. “Then…”
He looks back at Kokushibo with his wide, empty eyes.
“You look just like him,” Kokushibo says.
He doesn't kill Kamado that day, not when the sun has already risen. Instead he slumbers and waits for nightfall before he makes his way to what used to be the Tsugikuni estate. It takes him hours to retrace the route—he could barely remember his wife and children's names and faces, after all, of course his memory of the way home wasn't faring better.
But he gets there eventually and finds an abandoned house that's collapsed in on itself and overrun with plants. A few areas are intact, and that's the only reason why he knows this place is his old house. The three-tatami room Yoriichi and his mother used to stay in is still there (of course it is, everything related to his brother seems to have been preserved the gods' hands, somehow), and he recognizes the spot as muscle memory walks him down the path.
He slides the room open to dust and grime. Overgrowth has eaten up where his mother used to lay sick in her twilight years. Water damage has rotten where Yoriichi used to sleep.
He sits outside and watches the dust motes float around the empty room. If he closes his eyes, he can recall, in perfect detail, the hum of his mother's voice as she combs his hair and the soft shy wheeze of his little brother calling his name.
He returns to Mt. Kumotori a week later, after scrounging around the Tsugikuni estate for whatever clues he can find about his clan's strange connection to the Kamados. He hadn't looked back once after becoming a demon slayer; for all he knew, his father remarried, produced another child, and that's where the Kamados branched off.
There's nothing to find but rotten clothes and even more rotten rooms.
Kamado is waiting for him once more when he arrives, but he has no weapon in hand. Instead he’s sitting on the engawa with a lamp and a tray of tea.
“I looked into everything my ancestors left behind,” he says, in lieu of a greeting as Kokushibo stops a few feet away. “I’m sorry. There really wasn’t anything.”
The demon frowns, his lowest pair of eyes flicking to the tray of tea while the rest stay fixed on Kamado. “Where is your axe?”
That gets him another one of Kamado's blank-faced pauses. Eventually, the man speaks. “Sir, you look just like my father and grandfather,” he says. “And for the heirlooms of my family to have been crafted by your mother and brother…”
Kokushibo's teeth gnash.
Kamado exhales a sigh through his nose. “You are a demon.”
“Waxing One,” Kokushibo reminds. “Do you understand what that means?”
“Not fully.”
“It means I can tear you limb from limb, boy.”
Kamado quiets. His jaw doesn't tighten, he doesn’t tense—his posture betrays no unease like anyone else’s would have at such a threat. And it was all so maddeningly expected. Yoriichi always looked at him with such trust and awe, always held that worthless flute like it was the most precious thing he owned—kept it with him even on the day he set forth to fight Michikatsu.
“I don't know who you are, but you have something to do with my family,” Kamado finally says.
All six of Kokushibo's eyes narrow.
“May I ask about your brother?” he continues.
“Where,” Kokushibo grits out. “Is your axe?”
“...you are a demon.” Kamado lowers his gaze. Idiotic, to take one's eyes off the enemy. “But you may also be the only family I have left.”
Kokushibo nearly strikes his head off his shoulders right there. They don’t even know how they’re connected. What a fool to bow his head simply because of a possible familial connection.
So what if Kokushibo is possibly a distant ancestor? So what if he is possibly Yoriichi's descendant? He is a curse upon demonkind, a stain that must be wiped off the earth. Kokushibo has dedicated his entire life to overcoming his brother's achievements, and now it has been presented to him in physical form—
The weight of Yoriichi's broken flute seems to grow heavy against his side.
(“Brother, this is tragic.”)
He leaves without saying anything.
It's another year before he graces Kumotori with his presence. To his knowledge, Muzan has kept sending demons to Kamado, but still doesn't view him as that much of a threat to focus more powerful footsoldiers on him. Kokushibo has not heard of any slayers with hanafuda earrings either, so Kamado has stayed a simple civilian.
He climbs the mountain and stays by the forest to watch the Hinokami Kagura. Just like last time, Kamado shows improvement in his execution of the dance.
He also turns and bows to Kokushibo in greeting again. “Hello.”
“How have you been slaying the demons that man has sent your way?” Kokushibo asks instead of returning the attempt at friendliness.
“Ah.” Kamado straightens. “With my axe. I fight them until dawn.”
Of course.
“Do you not know of nichirin swords?”
Kamado shakes his head. “No, sir.”
“They are swords made with special ores. They soak in light from the sun, and that is what lets it kill demons when they are beheaded,” Kokushibo says. “They are also what is used for Sun Breathing. I imagine your ceremonial sword was created in emulation of that.”
His lowest pair of eyes flick to the seven-branched sword in Kamado's grasp. It looks just like his own sword when he alters it; some god is having a laugh somewhere right now.
“...I see,” Kamado says after another of his thoughtful pauses. “Where would one get a nichirin sword?”
This time, it's Kokushibo's turn to pause and think. When he had joined the corps, there hadn't been much organization. Breathing styles had just taken form, there were no kasugai crows to manage correspondence, and there wasn't as much secrecy with the locations. That had only changed after his betrayal and the next master decided concealment was a measure the Ubuyashikis and the swordsmiths would benefit from.
When he needed his sword repaired, he went to his swordsmith’s estate. Assuming the family is still in the corps' service despite their connection to him, they were probably squirrelled away in some mountain village.
“It has been years,” he admits. “Many things have changed within the Demon Slayer Corps' operation. Their swordsmiths are hidden.”
“Ah.”
Apparently, that's as much as Kamado has to say, as he proceeds to just stare. There are no pleas for Kokushibo to think of something else to remedy his lack of proper weapon, no musings of alternative measures.
Instead, Kamado motions toward his house. “Would you like to join me for tea, sir? The sun is quite high and it'll be too light out for you to travel safely.”
The nerve of this boy to invite the second most powerful demon in existence under his roof. Kokushibo can return to the Infinity Castle with a call for Nakime.
But Kamado waits for him, and it occurs to Michikatsu that the instinct that led him to sneaking into the three-tatami room to play with Yoriichi despite his father beating him for it is still there.
He joins him under the shade of the house.