By July of the eleventh year of the Ninja Era, the midday sun had become a physical weight, scorching the desert earth and warping the air over Sunagakure into shimmering mirages.
Inside Sengoku's stone house, however, the atmosphere was distinctly different, heavy with a quiet, intense concentration that completely shut out the oppressive heat.
The frayed edges of Simple Puppet Fabrication and Maintenance lay unrolled across the floor in front of him. For the past three months, Sengoku had balanced a punishing daily routine: physical conditioning, chakra refinement, and stabilizing his Rasengan. Every single drop of energy he had left over was poured into decoding this scroll.
He had burned every diagram, paragraph, and exact measurement into his memory. The text outlined the foundational blueprint for traditional humanoid puppets—how to craft articulating joints, route chakra thread pathways, assemble mechanical arms, and perform structural maintenance. It was a complete, highly logical system, representing the exact path walked by generations of Sunagakure puppeteers.
Understanding the theory was simple enough. But that was where its usefulness ended.
Sengoku looked away from the parchment, his gaze dropping to the empty stone floor as a nagging thought took root.
'Are humanoid puppets really the optimal solution?'
Mainstream puppetry—whether it was manipulating a heavy combat doll like Kankuro, or fielding a massive, venomous legion like the infamous Sasori—was entirely constrained by a biomimetic framework. There was an unspoken, collective assumption in the village that a puppet had to resemble a person.
Yet, the fragmented memories from his past life constantly hammered against this rigid, traditional thinking.
Why mimic human anatomy? Puppets didn't breathe. They didn't rely on muscle tension or leverage to generate kinetic force. Their movements were dictated entirely by the pull of chakra threads and the snap of internal gears. Replicating the human skeleton only introduced unnecessary fragility and manufacturing nightmares. Knees, spines, and necks provided natural agility for a living human, but on a wooden construct, they were glaring structural weak points waiting to be shattered.
Furthermore, against a high-speed taijutsu specialist, could a bulky, human-sized puppet actually keep up? Perhaps in the hands of a master, but the required control precision and material durability would have to increase exponentially to match that speed.
Sengoku was a seven-year-old orphan. His resources were practically non-existent, and his abilities were still in their infancy. Competing on the traditional, highly expensive path was tactical suicide.
Survival was the only metric that mattered. Every choice he made had to serve that absolute rule. He didn't need artistic imitation; he needed ruthless efficiency, stealth, and a lethal surprise factor.
His thoughts began to coalesce into a radical concept, one that would be considered complete heresy by the village's veteran craftsmen.
'Size… what if it was only as big as a handball?'
A construct that small would be highly portable and easily concealed in a standard ninja pouch. More importantly, the chakra burden required to manipulate it would be a fraction of what a large puppet demanded.
'Shape… form should follow function.' It didn't need arms or legs. A sphere? An oval? A simple polyhedron? Whatever best facilitated stealth and mobility in the air.
'Offense…' A miniature drone couldn't wield heavy blades or house massive flamethrowers. But there was one weapon perfectly suited for a compact, spherical chassis: the senbon.
Thin, lightweight, and completely silent upon launch. If the needles were coated in a common paralyzing toxin, they wouldn't even need to hit a vital organ. A mere scratch would be enough to cripple an opponent and dictate the outcome of a battle.
The blueprint clarified in his mind's eye: a fist-sized metal orb peppered with tiny, precisely angled firing ports. It didn't need heavy armor or a complex array of features. Its sole purpose was ambush and execution. While a single spherical drone might lack the overwhelming physical presence of a traditional puppet, a synchronized swarm of them flying through the air would be infinitely deadlier and harder to track.
The more Sengoku analyzed it, the more perfectly the unorthodox path fit his current reality. It demanded minimal raw materials, bypassed the need for complex joint articulation, and maximized lethality.
He glanced down at the intricate humanoid blueprints one last time. He felt absolutely nothing for them.
His goal today wasn't to forge a battlefield-ready weapon, but simply to prove the core concept. Step one was the hardest: miniaturizing the internal firing mechanism.
Sengoku reached for a small pile of prepared scraps he had scavenged—several thin, pliable iron plates and a handful of polished senbon. He picked up his carving tools and began shaping the metal. He didn't need a forge for this; the scrap iron was soft enough to work by hand.
Shutting out the searing desert completely, Sengoku sank his entire consciousness into the birth of his first creation.