Puppet Core Upgrade and the Modified Body Refining Furnace

The desert night was bitterly cold. A frigid moon hung in the ink-blue sky, casting its pale light across the boundless sea of sand and illuminating a concealed corner outside Shaye's team's temporary camp, hidden behind a massive sandstone outcrop.

Shaye sat cross-legged on the ground, a complex energy circuit blueprint spread out before him. Beside it lay an assortment of unusual materials: scraps of God Tree fragments recovered from ancient ruins, emanating faint energy fluctuations; a special metal discovered in the shattered ninja tool pouch of that Hidden Rock elite jonin during an encounter, exceptionally tough and capable of conducting chakra; and rare ores and timber he had traded for from the village warehouse or black market through his father's connections, using money saved from mission rewards and selling Spider puppets.

The search for the Third Kazekage had lasted for months without any progress. Instead, they had been running fruitlessly along the vast borders of the Land of Wind like headless flies. Intense battles, monotonous reconnaissance, hopes repeatedly igniting and dying out... such a high-pressure environment could nearly drive someone mad. Yet for Shaye, this constant travel and danger had also become a unique opportunity to test what he had learned and gather resources. After every battle, while clearing the battlefield, and every time he explored an unknown area, his eyes searched for anything that might help bring his grand blueprint to life.

His "theoretical knowledge" played an enormous role at this moment. His foundation as a mechanical engineer in his previous life gave him an understanding of materials science and energy conduction that surpassed that of local ninja. Meanwhile, the ancient Sealing Techniques and barrier knowledge he had learned from Bunpuku and Shukaku, along with the puppet core technology he had discussed with Chiyo and Sasori, provided the ninja world's means to turn that understanding into reality.

"The chakra version of the Body Refining Furnace is still far too inefficient." By the moonlight, Shaye lightly ran a finger over the central section of the blueprint representing the Puppet Core. The original Core could only perform basic chakra attribute energy conversion, transforming the ordinary chakra supplied by his father into energy better suited for nourishing the body, with a slight Yang attribute. However, both the conversion rate and energy purity were limited, making the process of repairing his foundation slow and impossible to sustain.

But the God Tree fragment he had acquired by chance, along with Shukaku's scattered remarks about natural energy, had opened a new door for him. Natural energy was everywhere, vast and boundless, and if it could be utilized... But the idea was far too dangerous. Directly absorbing natural energy was no different from suicide. His approach was to use the God Tree fragment as a primer and filter, designing a new type of Natural Energy Puppet Core that could slowly and safely draw in and initially tame natural energy, then use this upgraded Core to power the Modified Body Refining Furnace.

This required extraordinarily precise calculations and complex Sealing Formulae. Fortunately, patience and computational ability were what Shaye lacked least. On nights when his teammates retired early out of exhaustion and frustration, he often worked as he was now, sketching and calculating on scrolls with a specially made chakra-conducting pen by faint light. In his mind, circuit boards and energy converters from his previous life continuously overlapped and collided with the ninja world's sealing formulae and chakra meridian diagrams, sparking flashes of innovation.

This brief return to the village for supplies and rest was the crucial window for carrying out his upgrade plan.

A few days later, in Hidden Sand Village, inside the room in Shaye's home that he had converted into a simple workshop.

The doors and windows were tightly shut, and Shaye had even secretly set up simple barriers for soundproofing and blocking detection. The workbench was covered with an array of tools, while every kind of material had been sorted and arranged. Shaye's expression was utterly focused, his gaze sharp, and his hands steadier than those of an eleven-year-old boy had any right to be.

He first worked on the smallest God Tree fragment. Following methods he had inferred from Shukaku's words, along with the principles of advanced Sealing Techniques taught by Bunpuku, he carefully ground down the fragment's edges with a special solvent, producing a powder containing strange energy. Then, using refined gold as a base, he mixed the powder with other conductive materials and inscribed immensely intricate miniature barrier formulae. The process demanded astonishing chakra control. The slightest mistake could trigger an energy rampage or cause the formulae to fail. Shaye held his breath and concentrated, chakra threads spilling from his fingertips as fine as hair and precisely activating every node.

Only when the final rune lit up, steadily emitting gentle yet vibrant energy fluctuations, did Shaye let out a long breath. The core component of the new Core—the natural energy sensing and filtering module—was complete.

Next, he integrated this module with the chakra conversion module he had designed earlier, using the special metal he had collected as energy channels and casing. In the end, a "Natural Energy Puppet Core (Prototype)" was born—smaller than the original, yet several times more complex in structure, with a faint glow flowing over its surface.

With the Core upgrade complete, the next step was iterating on the Body Refining Furnace. He redesigned the energy circulation paths inside the furnace, allowing it to better accommodate the gentle energy flow mixed with natural energy produced by the new Core. He also added more materials to the furnace walls for stabilization and shielding. The new Modified Body Refining Furnace was slightly smaller, but its projected efficiency and safety had greatly improved.

At the same time, he had not forgotten his combat partner. The joint structure of the Big Spider puppet was further optimized, improving its load-bearing and cross-country capabilities. Most importantly, he attempted to apply his preliminary grasp of Magnet Release to Big Spider's movement system, adding simple magnetic levitation runes to its feet. While it still could not truly fly, this significantly reduced its weight, improved its speed and agility over sand, and lowered chakra consumption.

Everything was completed under the strictest secrecy. Although his father, Shaliu, knew his son was tinkering with something and offered whatever support he could, mainly materials and cover, he still could not help feeling his heart race when he saw the new Core radiating such an unfathomable aura. He repeatedly warned Shaye to be extremely careful.

When the rest period ended and the team set out once more upon the endless search, quiet changes were already taking place within Shaye's body.

After making camp each night, once safety was assured, he would activate the Modified Body Refining Furnace. The new Core no longer depended entirely on chakra supplied by his father or himself. Instead, like breathing, it began drawing in tiny strands of natural energy from the surrounding environment at an extraordinarily slow pace. After filtering and conversion, that energy mixed with Shaye's own chakra and became a warm current that continuously washed through and nourished his once-incomplete body.

The effects were obvious. His previously somewhat thin frame began to grow well-proportioned and upright at a visible pace. His muscle definition gradually sharpened, and his pale complexion was replaced by a healthy glow. The most noticeable change was his chakra reserves. The bottleneck that had once held him just before the Chunin threshold was shattered in one stroke, and his chakra continued to grow steadily, advancing toward greater depths. Though he was still some distance from a true jonin, both his chakra refinement speed and total reserves were no longer what they had once been.

Under the moonlight, Shaye finished a brief training session and slowly opened his eyes, the sharp gleam in his dark pupils restrained. He clenched his fist, feeling the surging power within him and an unprecedented sense of smoothness. He looked toward the deep night in the distance, his gaze seeming to pierce through the sea of sand and glimpse a broader stage in the future. The upgrades had only just begun. And ever-growing strength would be the foundation upon which he realized all his dreams in this turbulent ninja world.