In truth, Kimimaro had also wanted to learn the Yin Seal himself as soon as Ashina confirmed it was in his possession.
A technique that could stockpile otherwise wasted chakra, to be drawn upon at will, who wouldn't want something like that?
But Ashina had been clear, his tone carrying that faint sting of teasing.
The Yin Seal was an S-rank technique, legendary, yes, but available only to women.
Not by law, not by secrecy, but by nature itself.
It required softness, emptiness, the ability to nurture and yield, a quality tied to the female physique.
Kimimaro remembered the flat disappointment that washed over him then.
His immediate response had been sharp and to the point.
"Is there a Yang Seal version, then?"
Ashina's answer had been just as flat. No. Not in all of Uzumaki history.
No matter their brilliance in sealing, none had ever created a male counterpart to the Yin Seal. For some reason, it was simply inconceivable.
Kimimaro had thought about it long after. It made sense in a way. Only women were known to wield the technique.
Mito. Tsunade. Sakura.
Not Hashirama, who married Mito. Not Hiruzen, the so-called Professor, who claimed to know every jutsu in the village.
Not Minato, who had taken the Flying Raijin from Konoha's deepest vaults, the same place that should have also contained knowledge of the Yin Seal. None of them had ever used it.
That much made the conclusion logical: it belonged only to women.
But he hadn't been reconciled with that. Not at all.
He still pressed Ashina, refused to let it drop, even when told it was impossible. So Ashina had finally relented, handing him the method, letting him study it side by side with Reika.
Kimimaro had watched every stage.
The steady layering of seals for the adaptation over weeks.
The careful inscriptions and adjustments.
The long preparation, and at last, the final activation and subsequent first storage of the chakra.
He had seen it both through Reika's steady training and Emi's Byakugan-aided observations just weeks ago, here on Shūmoku while the cult business kept them anchored.
He had turned it over and over in his mind, searching for a path forward.
And recently, it had dawned on him.
"Yang Seal?", "So, who said I have to even store chakra?"
That was the first flash of thought that had lit in Kimimaro's mind, the spark that finally gave him a direction.
He had turned the idea over for days, brainstorming while observing Reika's Yin Seal process in detail, until the path became clear.
If the Yin Seal could not be inscribed on the male physique, then fine, forcing the same pattern would only end in failure.
But what if the seal wasn't storing ordinary chakra at all?
What if it was holding the chakra after it had already been reshaped, directly in its Yang-charged state?
Yang Release pre-formed chakra was denser, more vital, more concentrated than unshaped chakra, and most importantly, more fit for the male body.
A smaller reservoir could carry more power, and even if the male body lacked the "softness" to handle full Uzumaki-style storage, it might still withstand smaller, specialized containment.
Enough to matter.
When Kimimaro first proposed this, Ashina had been visibly unsettled.
He teased him at first, calling it reckless, but then the soul of the clan head fell into deep thought.
Days of discussion followed, back and forth, Ashina shocked at the sheer audacity of the idea. And slowly, reluctantly, even he admitted that with careful modification, it might actually be possible.
Kimimaro didn't even need vast oceans of chakra anyway. His greatest limitation wasn't raw reserves yet; it was safety.
Every time he pushed the Dead Bone Pulse too far, he shaved at his own life. The constant tearing, repairing, regrowing, a cycle of destruction that would eventually hollow him out.
What he needed most was fuel.
Yang Release–driven fuel.
External, assisted creation of his kekkei genkai's new osteoblasts and osteoclasts, the cellular machinery that grew and reabsorbed bone, multiplied outside of their natural pace.
If he could store pre-shaped Yang Release chakra in a seal, then call upon it in battle, he wouldn't need to spend precious time weaving it in the moment during dangerous battles.
It would already be there, ready to burn.
Not as grand as the Yin Seal, true.
It wouldn't turn him into a second Tsunade, sitting on an ocean of reserves.
But it was something else entirely: a weapon designed specifically for him, tailored to his body and his bloodline.
And this was only the beginning.
Chakra reserves could always be stolen.
After all, just by getting better at fuinjutsu and becoming a master, in the future, he could always directly siphon from others, perhaps even from tailed beasts themselves. Why not?
If even someone like Hidan could play a part in Akatsuki's jinchūriki hunts, personally capturing the Two-Tails somehow, at the right moment, then surely he, with planning and preparation, could do far more.
The options only multiplied the longer he thought. Exotic methods, dangerous roads, but all within reach, given enough patience.
And so, he and Ashina had debated, refined, and hammered the idea into a coherent form.
Just a few days ago, they had finalized the concept.
Soon, Kimimaro would attempt its inscription, after some finishing touches.
If successful, he would finally have the foundation he needed, a personal seal, his own mark, not the disgusting one borrowed from Orochimaru like the doomed original Kimimaro, but created by his own hand.
With it, the new Shikotsumyaku techniques he had imagined, destructive forms inspired by some ideas of his past life, would finally have fuel.
His strength would advance another step.
The curse mark of Orochimaru had made the first Kimimaro into a slave.
His own and Uzumaki-inspired seal would make him a master.
As for the other uses of a physical seal of that kind, like the massive chakra-assisted regeneration Tsunade had showcased, Kimimaro wasn't foolish enough to pursue that.
That path was a trap.
It would only make him a marauder of his own body, draining his lifespan with every cellular division.
His bones already carried that burden; doubling it would be suicide.
And he had no interest in ending up like Tsunade, who in her fifties looked a hundred without the mask.
Besides, his body already possessed heightened regeneration as a baseline. It had to.
Without it, the Dead Bone Pulse wouldn't even function. That was his worst-case safety net.
***
The ritual chamber was silent except for the faint hum of seals etched into the floor.
It wasn't the main cult hall but a side room, chosen precisely because its walls were thick and its light dim.
Incense burned faintly at the edges, mixing with the salty tang of Shūmoku's air.
Kimimaro sat in the center, bare-chested, his pale skin illuminated by the wavering glow of fuinjutsu lines spreading from a drawn circle beneath him.
His posture was calm, spine straight, but his eyes were sharp, the look of someone about to cross a line no one had ever walked before.
Emi crouched to one side, Byakugan veins bulging faintly at her temples, pale eyes scanning his chakra system with near microscopic precision.
"I'll see everything as it settles. If something goes wrong, I'll know before you do."
Reika stood on the other, her pendant glowing faintly with Ashina's voice flickering through it, invisible to anyone else but tangible in the way her golden eyes occasionally hardened when he spoke to her directly.
"You're not making me feel better," She murmured dryly at Emi, standing opposite her.
The brush in her hand moved with practiced precision, finishing the last strokes that would tie the array together.
Her pendant glowed faintly against her chest, Ashina's presence humming through it.
"Don't look for comfort," Kimimaro said, his voice calm, eyes shut. "Look for accuracy."
Emi rolled her eyes but smirked faintly. "Of course, lord accuracy himself. Remind me why I'm the one worrying about your skull splitting open?"
"Because you worry enough for both of us," Kimimaro replied, and there was the faintest flicker of amusement at the corners of his mouth.
Reika dipped her brush, finishing the line with a steady hand. "It's ready." She straightened, golden eyes settling on him. "One chance. Don't force it."
Ashina's voice rolled out from the pendant, deep and sardonic. "Remember, boy. You're not filling anything today. This is only the vessel. The slow accumulation comes after. If you try to shortcut it, you'll break yourself before you even start."
Kimimaro didn't move. His breath was slow, steady, his spine straight. "I understand."
The array flared as his chakra bled into it, Reika's inscriptions glowing with a faint light.
The lines contracted inward, sliding across his skin like living ink before sinking into him.
Emi leaned closer, her eyes tracking the way it merged. "It's not fighting him… no rejection. It's binding cleanly."
The glow rose, lines on the floor pulling inward, sinking into his skin. Emi frowned, leaning closer, scanning intently.
"It's stabilizing… no backlash. It's… merging."
At the center of his forehead, where he had always painted the old red ancestral dots, the glow sharpened.
The ink lines crawled up, then sank inward, leaving behind not paint but permanence.
The two dots remained, a darker shade of red and sharp, no longer decoration but true fuinjutsu inscribed into his flesh.
Reika straightened, wiping her brush. Her golden eyes lingered on him. "There. It's done. No more paint. They're yours now."
Kimimaro raised a hand, fingertips brushing the spots lightly.
He felt the hum beneath them, subtle but real.
The base of his seal. The beginning of something entirely his.
As the final strokes sank into his flesh, Kimimaro opened his eyes. "Emi. Guide me."
She leaned closer, pale eyes glowing, her voice calm despite the faint quiver in it. "Only a pulse. A ripple, not a flood. If you force too much, it'll rupture before it even begins to hold."
Kimimaro exhaled once, then drew on his Yang Release.
A faint golden warmth stirred in his coils, and he pushed it upward, carefully channeling it toward the newborn seal.
"Steady," Emi murmured, watching every line. "It's threading… yes… It's taking."
The two dots pulsed faintly in response, accepting the first wave.
Kimimaro's lips curved. "So it lives."
Reika folded her arms, her voice cool but edged with quiet relief.
"Then the foundation is set."
He exhaled, then activated the completed seal alongside the first wave of energy.
The dots flared black, glowing with condensed energy.
From them, markings spread outward, thin, dark lines branching like veins, trailing down his temples and curling across his chest and shoulders in elegant symmetry.
For a moment, the entire chamber seemed to breathe with the pattern.
Emi's eyes widened, her Byakugan drinking it in.
"It's… perfect. No leaks, no cracks. It's fused."
Kimimaro's own lips curved into a small, sharp smile. "As expected."
Reika crossed her arms, though her voice was softer than usual.
"So you've done it. The first step."
Ashina's chuckle rolled through the pendant, half-pride, half-mockery.
"You've written your own mark into history. Fitting. But don't grow arrogant. Now begins the long work of filling it, drop by drop."
Kimimaro ignored him, letting the glow fade.
The black lines receded until only the two dots remained, permanent, symmetrical, as if they had always belonged there.
No more red paint. No more pretense.
"When dormant," he said quietly, almost to himself, "it is nothing but these. But when called upon…"
The grin sharpened. "…then it becomes mine."
Reika looked at him for a long moment, lips pursed, a strange softness flickering in her golden eyes.
Emi, meanwhile, muttered under her breath, though her relief was clear.
"You really scared me for a second there, you lunatic. Who carves seals into their own skull?"
Kimimaro rose, cloak sliding back onto his shoulders. "Only the ones who plan to outlive everyone else."