One of the guild compound's warehouses—a high-security facility—doubled as Hii Kōri's private workshop.
The low hum of machinery echoed through the cavernous space, illuminated by shadowless lamps that left no corner dark. Rashōmon, uncomfortable in the unrelenting light, had retreated to a small sprout-like tendril poking out from Hii Kōri's collar.
Hii Kōri was assembling a puppet's skeleton.
Neat rows of precisely machined parts lay on the workbench before him, picked up and fitted together by robotic arms.
From the very beginning of the design phase, he had prioritized modularity.
In his design, aside from specific structural components and weapon configurations, the majority of parts—support structures, joints, drive systems—could be shared across puppets of similar size.
This approach had added enormous complexity to the planning stage, but the benefits were obvious: with sufficient stockpiled parts, maintenance, repair, and even field reconfiguration would be dramatically faster.
Even more, the modularity would allow for greater adaptability, letting him reconfigure the puppet's form on the fly.
Technology's greatest strength was reproducibility. Even if one didn't understand the underlying principles, following the process exactly would yield the same results.
Saying "only I can make this" might be a form of secrecy, but that wasn't how industrial production worked.
Process limitations could be overcome material limitations were the real bottleneck.
In truth, Hii Kōri wasn't worried about his blueprints being stolen. Even if someone fabricated the parts, they could never obtain the finished product.
The parameters on those blueprints were calibrated specifically for materials he had personally processed.
The structural components for the outer armor and core parts were made from "nonexistent metal"—materials he had completely transformed, imbued with multiple properties. The skeleton parts, while less extensively modified, still had altered parameters: enhanced toughness, greater strength, chakra conductivity, and compatibility with cursed energy.
Even the conductive pathways etched onto the skeleton's surface were, in truth, a decor—an ornamental lining, if you will.
A Master Grade GINN would weep with envy.
From what was already assembled, the skeleton was clearly avian. The main body stood about a meter taller than Hii Kōri, with a wingspan of four to five meters even before plating.
On a nearby workbench, a small slug—much smaller than the one Tsunade had summoned earlier, only palm-sized—lay quietly, watching Hii Kōri's fluid movements with interest.
As the bird-shaped skeleton took shape, she voiced a gentle question: "Hii-sama, this puppet seems too large to control with conventional chakra threads."
"And judging by the internal structure, there doesn't seem to be space for a pilot?"
During the war, when Hii Kōri had been searching for Dan Katō, she had seen the large puppets he had left behind.
Those machines had left quite an impression.
"That's intentional. This series is designed to be autonomous—no external control required."
Hii Kōri operated the robotic arms, locking a wing bone into place as he explained.
"Autonomous mechanism, is it?"
The slug wiggled its eyestalks, repeating the term.
Having been contracted to Tsunade before the war, the slug had little interest in human conflict, but had nevertheless absorbed much information.
Puppetry was a technique Sunagakure had developed to compensate for its deficiencies in both manpower and variety of techniques.
For all its advantages—excellent endurance, resource efficiency, versatility, adaptability to different environments—it had one critical weakness: the puppeteer required chakra threads to control the puppet's limbs.
The pinnacle of puppetry, as far as the current era was concerned, was Chiyo's White Secret Technique: Chikamatsu's Ten Puppets—the Ten-Finger Technique, each finger controlling a separate puppet.
Even in the original story, Sasori—who had transformed himself into a puppet—still needed to extend chakra threads from his core to control the hundreds of puppets in his Red Secret Technique: Hundred Puppet Performance.
While the sands of the Land of Wind could hide this weakness in local battles, if the enemy had already reached their homeland, why not use the more powerful Sand Manipulation techniques instead?
In any case, a puppet requires at least one chakra thread.
The gap between "one" and "none" was absolute.
What Hii Kōri wanted to create was not that.
Even before the Second Shinobi World War began, he had used permanent magnet cores—produced through Magnet Release—to create semi-autonomous machines that could follow simple instructions, establishing Red Hot Sand's first production line.
"I see. So the large amount of energy Hii-sama mentioned earlier was for this."
The slug recalled their earlier conversation, her tone brightening with something like pride at having guessed his intent.
"Mm-hmm. Exactly."
One hand tapping buttons on the workbench, the other idly toying with Rashōmon's sprout-like tendril, Hii Kōri responded in the same light tone.
Autonomous dolls were a staple of manga and games.
But whether they ran on some special energy source or gained power from intricate mechanical structures, the explanations were always vague—barely useful as reference.
Yet in the world of his previous life, there had existed true autonomous puppets that required no external input.
Cursed corpses—or rather, fully autonomous cursed corpses.
One could not mention cursed corpses without mentioning Yaga Masamichi, principal of Tokyo Jujutsu High.
As his name implies, he was a man who walked the straight and narrow. Despite his stern, intimidating appearance, he was a passionate educator.
In Hii Kōri's previous life, Yaga had been his teacher. Yaga had always felt he had failed as an educator, unable to guide his brilliant student properly.
But from Hii Kōri's perspective, the fact that he hadn't become a full-blown antisocial criminal was thanks to Yaga's teaching.
On that matter, his teacher bore no blame.
Yaga was recognized as the foremost expert in jujutsu puppetry. He could create cursed corpses that operated independently without any external cursed energy—and even possessed self-awareness. His masterpiece was Panda, the puppet he regarded as a son.
Beyond that, Yaga had also mastered the technique of imprinting a deceased person's soul data onto a cursed corpse, preserving their memories.
In a sense, he had brushed against the boundaries of two forbidden domains: artificial life creation and resurrection of the dead.
Though Yaga publicly claimed Panda was a "sudden mutation," an unrepeatable accident—refusing the title of Special Grade on that basis—
Hii Kōri knew the truth: it was a fully mastered technique.
His teacher had likely made that claim knowing how the higher-ups of the jujutsu world operated. He hadn't wanted the technique to fall into their hands, to be used for more atrocities against ethics.
As Yaga's student—and a top-tier craftsman himself—Hii Kōri had refrained from inheriting his teacher's cursed corpse techniques for similar reasons.
Given his younger self's character—pursuing technological advancement without regard for ethics—the impact of those techniques in his hands might have been even worse than in the hands of the jujutsu higher-ups.
That didn't mean he couldn't infer the principles and adapt them.
Copy all information from body to soul, imprint it onto the cursed corpse's core. Then place multiple compatible pseudo-souls into the core, letting them observe each other to stabilize and awaken self-awareness.
Once the soul is fully formed, it would generate cursed energy spontaneously, like a cursed spirit or sorcerer.
But Hii Kōri didn't intend to give his puppets personalities. Rashōmon—born to test a concept, and never meant to be treated as mere tool—was one thing. Giving a simple tool a personality was… awkward.
That was why he had approached the problem of "self-sustaining energy core" from a slightly different angle.
The semi-autonomous puppets on his production line, for example, were powered by permanent magnet cores. They maintained their charge by interacting with the ambient magnetic field.
"Like oil droplets on water. If there's one large droplet, the smaller ones will gradually be drawn to it."
Hii Kōri wiggled his fingers, tracing patterns in the air. "I've already built three different chakra cores in my body—neutral, Yin, and Yang—forming a constant cycle of Yin and Yang Release."
"If I expand that cycle to the surrounding environment… I can complete a cycle of natural energy. With a stable core that has sufficient 'gravity,' as long as instantaneous output stays below a certain threshold, this puppet will no longer need external energy input. It will be a truly autonomous mechanism."
"Remarkable. Hii-sama's chakra cycle system is almost identical to how the Sacred Lands operate."
The slug raised its body, surprise evident in its tone.
"Flow and cycle are my specialty, after all."
"Then what will Hii-sama use as the natural energy storage core?"
The slug sounded eager. "If you need, we can act as the component."
"I'm not about to use a newly contracted ally as biological wetware. That would be ugly. And it wouldn't be a perpetual motion autonomous mechanism, would it?"
Hii Kōri was momentarily speechless at the slug's rather intense suggestion—whether this was "birds of a feather" or "keeping bad company," he couldn't say.
"My original plan was to use a tailed beast's nearly inexhaustible chakra as the energy source, then isolate its consciousness. But right now, I can't get any tailed beasts other than Shukaku. I needed a temporary solution."
With that, he retrieved a pendant from the scroll on his wrist.
It was the same pendant that carried the lingering wills of his birth parents—capable of storing any known type of energy.
During the war, even with the stored chakra as backup, firing the shot that had annihilated thousands of Konoha ninja had still cost him seven or eight years of his lifespan.
But now, just a year or two later, he hardly needed it as a backup power source anymore.
Yang Release was good. You had to practice it.
For now, though, this pendant remained an excellent "battery" option.
"Please fill this with some natural energy, Katsuyu."
Hii Kōri handed the pendant to the slug. She readily agreed, leaving behind a smaller division before returning to Shikkotsu Forest with a poof to "fill the tank."
Unlike other summoning creatures, the slugs of Shikkotsu were all divisions of the main Slug Sage. Each division had its own consciousness, yet they shared a subtle connection.
Though they couldn't convey detailed information through this link, passing simple notifications was possible.
About twenty minutes later, when Hii Kōri had nearly finished assembling the puppet, the smaller slug suddenly returned to Shikkotsu as well—and he immediately summoned Katsuyu back.
"Let's see if this is enough."
The slug arched its body like a cat showing off a prize, offering the pendant—now charged with a vast amount of natural energy.
With a nod, Hii Kōri took the pendant and inserted it into the bird-shaped skeleton through an opening in the unarmored chest, fitting it into a small cube.
Under his control, the cube dissolved into countless particles that swirled around the pendant, absorbing it, then re-formed.
He formed a Chakra Scalpel, cut his palm, and smeared blood over the cube. Countless seals spread across the skeleton. The pendant within activated, releasing a surge of natural energy.
Hii Kōri withdrew his hand; the chest armor closed. Then, the crystals on the bird's claws, wings, and crest lit up one by one—golden light, like molten gold, flowed through the circuits etched into the outer armor.
With a sharp cry, the living mechanism stretched its joints—stiffly at first, then smoothly. It spread its wings and took flight!
In seconds, it adapted to its own form, soaring through the workshop in elegant loops, performing complex maneuvers before landing beside Hii Kōri, crouching obediently, awaiting its master's inspection.
"Hmm… energy consumption rate 3.62%, conversion rate around 2.14%, brake system… accounting for weapon output…"
Hii Kōri stroked the bird's neck, reading data from its internal sensors, calculating various parameters. After a moment, he smiled. "For a first test, these are excellent results~"
"Is that so? Then congratulations, Hii-sama."
The slug couldn't quite interpret the numbers, but if Hii Kōri was pleased, that was good.
"Speaking of which, have you named this puppet?"
"Of course."
Hii Kōri stretched, then reached out to let the slug climb onto his shoulder.
Though he was more comfortable building beast-shaped puppets, the morning sun he had watched earlier had moved him somehow.
Looking at the mechanical bird awaiting his command, he spoke its name softly.
"Mechanized Bird: Tokoyo no Uzume no Naganaki."
***
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