The desert night was biting cold, a dry, crystalline chill that made standard lubricants seize and traditional puppet joints groan. A pale, indifferent moon hung over the indigo sky, spilling silver light across the endless sea of sand. It illuminated a hidden nook sheltered by an enormous, wind-eroded rock on the extreme edge of Team Iryō's makeshift camp.
Inside that nook, I sat cross-legged, the air around me shimmering with the heat of a single, flickering oil lamp. Spread before me was a complex energy-circuit blueprint, a masterwork of overlapping logic from two worlds. Scattered around were the raw materials of my ambition: off-cuts of the "Unknown Fragment", which I was now certain was a shard of the Divine Tree, gleaned from that ancient rock fissure; high-grade chakra-conductive metal harvested from the gear of the Iwa Elite squad we'd just deleted; and rare ores I'd spent months bartering for through my father's logistics connections.
The hunt for the Third Kazekage had dragged on for nearly half a year, a mission that had become a recursive loop of futility. We were blundering like headless files across the Land of Wind's vast border, our morale dropping with every empty canyon we searched. But for me, the grind was a resource-gathering phase. Every post-battle sweep was a chance to "harvest" high-end components. Every venture into the unknown was a "beta test" for my theories.
The original Body Tempering Furnace has hit its ceiling, I thought, tracing a finger over the "Puppet Core" module on my blueprint.
The Gen 2 core was a purely chakra-powered device. It performed basic chakra-element conversion, turning my father's ordinary, earth-heavy energy into a faintly Yang-tinted stream suited for biological repair. It worked for "bug fixes", patching the defects of my premature birth but its throughput was too low for a total system overhaul. It was a 5-volt solution for a 10,000-volt vision.
The acquisition of the God Tree shard changed the project scope.
Shukaku's grumbling about "Natural Energy" had provided the missing line of code. Natural Energy was the planet's original power source, omnipresent and infinite, but it was raw and violent. Trying to absorb it directly was like trying to download a petabyte of data through a dial-up modem, your hardware would literally melt. I needed "Middleware." I needed a "Spirit Siphoning Seal" to act as a step-down transformer.
The build required a level of precision that made my hands ache just thinking about it. I spent the quiet hours of the night sketching and solving by the dim light of the lamp. In my mind, the circuit board layouts from my life as Logan overlapped with the sealing formulae of the Ninja World.
If I use the shard as a lure and a filter, I reasoned, I can craft a 'Hybrid Core' that draws and pre-tames Natural Energy, then let that upgraded core drive the furnace.
The return to Sunagakure for resupply was my manufacturing window. Inside my room, now a heavily shielded workshop bristling with silencing barriers I went to work. The workbench was a chaotic landscape of tools and sorted ores. I used a special solvent to grind a microscopic sliver of the God Tree shard into a powder that hummed with a frequency so high it made my teeth vibrate.
I didn't breathe. I used hair-thin chakra threads to inscribe microscopic array patterns onto an adamantine-alloy base. One slip in chakra control, one micro-second of lag in my concentration, and the shard would trigger an energy surge that would level the entire block.
When the final rune flared, emitting a gentle, life-rich pulse of pure white light, I finally exhaled.
The Natural Energy Puppet Core (Prototype) was online.
It was palm-sized, its surface rippling with a soft, milky radiance. It felt alive. I integrated it with the furnace's energy conduction system, rerouting the internal flows to better suit the hybrid stream the new core produced. I replaced the old copper wiring with the high-purity Iwa metal, increasing the "bandwidth" of the energy delivery by 400%.
I didn't stop at the furnace. I looked at the "Great Spider" sitting in the corner, its wooden joints scarred from the fight in the riverbed. I used my nascent Magnet Release to etch Magnetic-Levitation Runes into its leg joints. It wasn't true flight, the energy cost for anti-gravity was still astronomical but I could now "lighten" the chassis by 60%, eliminating friction and boosting speed to a level that mechanical gears could never achieve.
The break ended, and the "Sandstorm" squad set out once more across the dunes. My teammates saw a healthier version of Sayo, but they didn't see the "Reactor" humming inside my pack.
Each night, I activated the furnace. I'd lie inside the metal cylinder, the hatch hissing shut to create a total sensory deprivation environment.
"Boot sequence: Initialized," I whispered.
The new core began to "breathe," drawing in wisps of Natural Energy from the surrounding desert air. The Spirit Siphoning Seal filtered the raw power, stripping the environmental "noise" and converting it into a steady, warm current of pure vitality.
The experience was unparalleled. It wasn't the gentle repair of the old system; it was a fundamental evolution. I could feel my cells greedily absorbing the nectar, becoming more resilient, more dense. My meridians weren't just being "patched" they were being widened and reinforced, rebuilt with a "high-pressure" architecture. My bone density increased, my muscle fibers reorganized for maximum torque, and my metabolism moved toward a more perfect, efficient state.
And then, there was the chakra.
With the foundation repaired and the "bandwidth" of my meridians increased, my spiritual and physical energies fused with a smoothness I'd never known. A volume of chakra far mightier and more boundless than before surged through my system like a bursting dam. The bottleneck that had stalled me at the Chunin-level for years was obliterated.
Chakra status: High-Chunin... climbing... reaching Low-Jonin threshold.
Moreover, this newborn chakra, because it was born from a Natural Energy hybrid, felt purer and more agile. I could "broadcast" it with minimal loss. My control over Magnet Release wasn't just a "lever" anymore; it felt like I was holding the keys to the world's physical laws.
Under the moon, I emerged from the furnace, my body steaming in the cold night air. I stood taller. My complexion was robust, my eyes flashing with a calm, analytical gleam. I clenched a fist, and the air cracked with a slight sonic boom not from a jutsu, but from raw physical torque.
"System status: Optimized," I murmured.
The upgrade was only the first phase. My body was finally a high-spec machine, and my mind was the ultimate user. Looking out at the dark desert, I realized I wasn't just a ninja in a war anymore. I was an engineer with a blank canvas.
The path ahead had a new direction, and the "Mirage" project was finally moving into the hardware phase. The Third Great Ninja War was gathering speed, but for the first time, I felt like I was the one writing the rules of the encounter.