The concept of the Body Tempering Furnace was a beacon in my mind, but the closer I got to it, the more I realized how treacherous the terrain was. A blueprint is just a dream if you don't have the materials to build the foundation, and my first and biggest problem was still energy.
Chakra was everywhere, but it wasn't "clean." Chiyo's warning was always in the back of my head: foreign chakra is basically poison because of the spiritual "metadata" attached to it. If I wanted to use it to rebuild my body, I couldn't just pump it in. I needed a way to strip the signature, harmonize the frequency, and turn it into pure, neutral life-energy.
I looked into Medical Ninjutsu again. Yang Release was the closest thing to what I needed, it's the energy of life and growth. But Medical Ninjutsu usually happens inside a person. How was I supposed to build an external device that could take a raw, violent Wind or Fire nature and transmute it into a gentle Yang-stream? It sounded like a fairy tale.
I buried myself in the workshop archives, but most of Suna's records were focused on killing things with wooden puppets, not fundamental energy theory. I sketched out a dozen "rectifier" circuits, using seals to guide the flow, but the math never checked out. The efficiency was trash, the dissipation was too high, and the attribute conversion was sloppy. One glitch in the code and I'd be pumping "Fire-flavored" poison directly into my heart.
I hit a wall. I needed something more advanced something that touched the bridge between "machine" and "life."
So, I went back to the only person in the village who was crazy enough to try bridging that gap: Sasori.
I knew it was a gamble. Sasori didn't "do" favors, and he certainly didn't like sharing his proprietary tech. But I had a plan. I didn't go in asking for help; I went in with a "bad" design a simplified, edited version of my conversion circuit. I presented it as a way to improve the "energy efficiency" of a standard puppet core.
As expected, Sasori didn't even look up before he started tearing my design to shreds.
"Stupid," he muttered, his carving knife never missing a beat. "Inefficient. These seal nodes are redundant; you're losing 15% of your output right here. And this conversion layout? Laughable. You're trying to force different attributes into a fixed pattern like you're domesticating a wild animal. Chakra isn't dead data, kid. It has its own 'will.' It won't be bound by a simple seal."
His critique was brutal, but it was exactly what I needed. He'd just pinpointed the three biggest flaws in my logic. I didn't argue; I just took notes and asked the follow-up question I'd been rehearsing for days.
"Senior Sasori... is there a core design that can 'intelligently' handle the energy? Something that simulates vital activity to manage the flow better?"
I was pushing my luck. That question brushed right against the edge of his secret research into the Human Puppet.
Sasori's hand stopped. He actually looked at me really looked at me for the first time. Those purple eyes were deep, cold, and calculating. The workshop went deathly silent.
After a long minute, he let out a short, dismissive snort. He stood up, walked over to a dusty, forgotten corner of his scroll rack, and tossed a tattered piece of parchment at my head.
"A garbage idea," he said, returning to his bench. "But if you're determined to waste your time, look at that. It's a collection of early concepts on 'Regeneration Cores' crude theories on energy vitality and mimicry. I threw them away years ago. Read it, destroy it, and stop bothering me."
I caught the scroll, my heart hammering. I gave him a deep bow he didn't see it, or didn't care and sprinted out of the courtyard.
Back at my desk, I spread the scroll open. It was a mess hurried notes, failed experiments, and half-baked hypotheses. But it was gold. It talked about "Energy Resonance" and "Mimicry Cycles." To Sasori, these were "discarded failures." To me, they were the missing lines of code for my middleware.
I didn't need a full-blown Regeneration Core. I just needed a "Harmonizer."
Inspiration hit me like a physical blow. I grabbed a fresh scroll and started drawing. I combined my old-world knowledge of transformers and rectifiers with Sasori's "mimicry" logic.
I ditched the idea of "forced conversion." Instead, I designed a core that used my own dual-nature (Wind and Earth) to create a "Resonance Field." Any chakra entering the core would be broken down by the field, its personal imprints shattered by the vibration. Then, the neutral energy stream would enter a micro-cycle based on Yang Release theory nurturing it, smoothing it out, and turning it into a stable "Life-Energy" fuel.
It was guidance, not force. It was high-efficiency, low-waste, and most importantly, it was safe.
The pen flew across the paper. I mapped out the internal conduits, the resonance nodes, and the final output stage. My brain was running at 100%, fitting the pieces of three different worlds into one cohesive machine.
When I finished, I sat back and breathed.
I looked at the blueprint a perfect synthesis of engineering and magic. It was the first "real" component of the Body Tempering Furnace. It was the key to my survival.
I whispered the name I'd written at the top of the scroll.
"The Puppet Core."