Konoha Year 45. The last twelve months felt like they'd been played at double speed. I hadn't grown much, I was still the scrawny, pale kid in the back of the room but the "resolution" in my eyes had changed. I wasn't just looking at the world anymore; I was analyzing it.
I poured every spare second and every spare cent into the project codenamed "Core." The profits from my Spider sales, combined with whatever credits my dad could scrape from his combat pay, vanished into the workbench. I was buying tiny specks of chakra-conductive alloys, high-sensitivity crystals, and experimental heat-shielding. My desk looked less like a ninja's room and more like a high-end clean room in a tech startup.
The transition from blueprint to hardware was brutal.
On paper, the logic was perfect. In reality? Gravity, friction, and thermal expansion don't care about your "perfect" math. I had to do most of the work by hand with primitive tools, grinding away at the metal millimeter by millimeter.
I failed. A lot.
If I messed up the etching on an energy circuit by a fraction of a hair, the whole core's resonance frequency would drift, making harmonization impossible. If I used the wrong soldering temp, the different metals would crack the second I fed in a test wisp of chakra. The micro-circuits I'd borrowed from Sasori's "garbage" theory were even worse they clogged or collapsed every time the energy flow hit a certain pressure.
Every failure was expensive. Every crack in a crystal meant a week's worth of Spider sales literally went up in smoke.
But I didn't stop. I treated every failure as a debug log. I analyzed the data, revised the "code" on my blueprints, and tried again. My memory was my best tool I never made the same mistake twice.
I also got sneaky with my "consultants."
I'd go to Granny Chiyo with "innocent" questions about chakra equilibrium. She'd answer from a medical perspective, giving me tips on energy balance that I'd immediately translate into my structural designs.
Then I'd go to Sasori with a modified part never the whole thing and ask about stress loads. He'd look at it, call it "garbage work that will shatter in three moves," and then sketch out a fix that was so ingenious it made my brain hurt. He was dripping with sarcasm, but his "sarcasm" was full of master-level engineering secrets.
I was stringing together pearls of wisdom from the two best puppet masters in the world, and they didn't even know they were helping me build a "super-soldier" furnace.
My dad was my silent investor. He didn't understand the diagrams or the energy theories, but he saw the circles under my eyes and the growing pile of scrap metal. He stopped asking questions and just started sending more money, using his frontline connections to "liberate" rare materials that weren't available to regular apprentices.
Finally, on a cold night under a desert moon, I finished the last step. I sealed the complex micro-circuits with a special conductive coating and took a deep breath.
I focused a tiny, needle-thin wisp of my Wind-Earth chakra at my fingertip and touched it to the walnut-sized metal sphere.
There was no explosion. No hiss. No smoke.
The sphere's etched patterns slowly lit up with a soft, steady blue glow. The internal field activated, and I felt a faint, rhythmic pulse like a heart beating in slow motion.
It was drawing in my messy, attribute-heavy chakra, channelling it through the resonance loops, and outputting a thin, pure stream of neutral life-energy. It was attribute-less. It was clean. It was safe.
Success.
I sat there for a long time, just watching it glow. More than a year of sleepless nights and expensive failures, and it finally worked.
It was just a prototype. The conversion efficiency was terrible maybe 20% and the output wasn't even enough to power a desk lamp, let alone a Body Tempering Furnace.
But the theory was proven. The "middleware" existed. I'd successfully built a hardware bridge between raw chakra and biological repair.
I picked up the warm little sphere, feeling its pulse against my palm. I was exhausted, but for the first time since I woke up in Suna, I felt like I was actually winning.
The road ahead was still long, but the lights were finally on. I had my core. Now, I just had to build the machine around it.