Inside the wind-carved rock cave, the air didn't just feel still; it felt solidified, as if the very atoms were resisting the tension between the two occupants. Sayo stood in the center of the cavern, framed by the sparse, dusty natural light filtering through the rock fissure. Opposite him, Sasori remained seated at his workbench, the silence between them a heavy vacuum that sucked the warmth out of the room. Time had moved forward for both of them, but it had etched vastly different marks upon their systems.
Sayo stood tall, his posture a testament to a year of continuous "Biological Debugging." The deep nourishment provided by the Natural Energy Body Tempering Furnace Mk-III had thoroughly deleted the traces of his early frailty and illness. He had finally outrun the "Premature Infant" origin story. His height now surpassed most of his peers, and his physique was a masterpiece of well-proportioned, slender power. His muscle lines were smooth and high-torque, neither bulky like a brute nor weak like a scholar. His skin had the healthy, vibrant glow of someone whose metabolism was running at peak efficiency.
With his dark eyes fixed on his former mentor, Sayo radiated a restrained brilliance. To any observer, he was a burst of life toward perfection, a "System Rebirth" that had shed the mortal coil's limitations.
Sasori, however, had moved toward the opposite extreme.
His fiery red hair remained striking, but it was disheveled and matted with the dust of the badlands, falling across his forehead in sharp, jagged shadows that amplified his gloomy aura. His face eerily maintained the handsome, delicate features of his youth, but the quality of the "texture" was wrong. His skin was too smooth, lacking any blood color or thermal signature; it presented an inhuman, porcelain-like texture that didn't catch the light so much as absorb it. Most unsettling were his violet eyes - cold, hollow gems that reflected the cave's interior but refracted no inner emotion.
Sasori wore a long black traveler's robe, the wide sleeves obscuring much of his frame. His right hand, which had slowly lowered the carving tool, was no longer flesh. It was a precisely structured, multi-jointed puppet prosthesis of dark mahogany and inorganic metal, gleaming with the cold, sterile light of a machine.
But as Sayo's thirty-year-old soul, the mind of Logan, scanned the figure, he realized that the visual changes were just the "Frontend" of the transformation. The "Backend" was far more terrifying.
Sayo's perception was exponentially more acute than it had been six months ago. After the baptism of the Natural Energy furnace, his ability to sense life-force and energy frequencies had become a high-resolution diagnostic tool. He focused his senses on the figure before him, and his internal "HUD" suffered a total data-crash.
He could barely perceive a biological signature.
Within Sasori's body, there was no surging vitality of blood, no rhythmic life-force field, and no thermal output from a beating heart. Even his breathing was a shallow, stagnant cycle that served no respiratory purpose. Instead, centered in the middle of his chest, Sayo sensed an extremely condensed, frigid, and overwhelmingly vast chakra core. It was a cold energy furnace, pulsating with a mechanical rhythm, driving the "Perfect Shell" around it.
Sayo understood the "Change Log" instantly. Chiyo's whispered fears, the forensic evidence of the Third Kazekage's disappearance, and Sasori's obsession with "Eternal Beauty" had all culminated in this.
Sasori had successfully compiled the Regeneration Core.
He had executed a total system migration. He had abandoned his perishable human hardware, transferring his consciousness, his brain-data, and his chakra circulatory system into a self-made, eternal energy core. The being sitting at the workbench was not a "Ninja" in a black robe. It was a meticulously crafted Human Puppet, a high-spec chassis driven by a soul-carrying reactor.
"It seems..." Sasori's cold, hoarse voice broke the suffocating silence. He slowly raised his prosthetic right hand, the five fingers flexing with a high-pitched, mechanical whir that echoed against the stone. He scrutinized Sayo with the detached appraisal of a developer looking at a competing product. "The Village's food is quite good. It's made you, this little mouse, look quite... presentable."
His tone carried an inhuman indifference, a condescending scrutiny that treated Sayo as an insignificant object that had accidentally received a high-tier update.
Sayo suppressed the instinctive chill crawling up his spine, forcing his voice to remain flat and clinical. "Senior Sasori, your changes... appear to be even more fundamental than mine."
Sasori's lips curved ever so slightly, a mocking arc on a lifeless face that appeared particularly eerie in the gloom. "To pursue eternal art, one naturally needs to discard boring and perishable flesh. It seems you are still obsessed with this low-level, self-deceiving growth of life. You've patched your body, but it is still a system that will eventually rot and crash."
His gem-like eyes swept over Sayo's well-proportioned figure, as if looking at an imperfect semi-finished product that had wasted its processing power on irrelevant aesthetics.
Sayo ignored the mockery, taking a deliberate step forward. He needed to test the "Interface" of this new Sasori. "I didn't come here to debate the merits of art or hardware longevity, Sasori-senpai. The Village is currently in a state of 'Critical Failure.' The Daimyo has cut our resources, and the Fourth Kazekage is--"
"Shut up."
Sasori's voice suddenly became sharp and cold, cutting through Sayo's words like a razor-wire. The mention of the Kazekage seemed to trigger a "Security Exception" in his mind. The temperature in the rock cave plummeted, and a faint, violet chakra began to leak from his joints.
"That Village, that position, the 'Legacy' of the Sand... it has been deleted from my active processes," Sasori said, his voice vibrating with a lethal, metallic resonance. "If you came here to talk about these boring, legacy matters, then you can leave now, before I decide to turn you into a new collection. Your current hardware... it might actually be worth preserving in a display case."
The atmosphere in the cave instantly hit combat-readiness. Sayo looked at the familiar yet alien puppet body before him, a complex storm of data and emotion whirling in his mind. He realized that Sasori hadn't just defected from Sunagakure; he had "Formatted" his own humanity. He had severed every link to his past to embark on a lonely, obsessive path of mechanical divinity.
Logan looked at Sasori, and then at his own hands. They were two different philosophies of engineering. One embraced the evolution of life and the harmony of Natural Energy. The other pursued the cold, unyielding silence of eternity.
"Evolution vs. Stagnation," Sayo whispered to himself.
Sasori stood up, the joints of his porcelain body clicking with a sound that signaled a total lack of friction. He wasn't a mentor anymore. He was an S-rank anomaly with a "Regeneration Core" that Sayo desperately needed to study, if he could survive the encounter.
The reunion was over. The "Stress Test" was about to begin.