Ryuki Sato stepped across the jagged line where shattered glass met rusted structural steel. The lobby of the ancient KaibaCorp regional facility smelled of dried mud, burnt wiring, and decades of stagnant dampness. His boots made a sharp, wet crunch against concrete pulverized during the city's collapse. Exhausted as he was, he goes to a surviving pillar that still standing tall. Ryuki leans against it and taking a deep breathe. Above him, a massive vaulted ceiling hung twisted like the exposed ribs of a dead leviathan. The daylight behind him barely reached ten paces into the gloom, choked out by towering piles of fallen concrete slabs. Then, a sharp chime echoed through the sub-floor. Click. A strip of recessed LED lights along the baseboard flashed once. Dust danced in the sudden, hard beam of blue-white light. Ten yards deeper down the left hall, a second strip hummed awake, followed by a third, stepping down the dark corridor in precise, one-second intervals. Ryuki pulled his makeshift cloak closer around his shoulders. His right arm throbbed, but it was not the searing heat of his crimson mark. It was a faint, high-frequency vibration that ran up through the soles of his boots and rattled the teeth in his jaw. He didn't look back toward the outer desert. He followed the lights. The floor sloped downward at a steady decline. Overhead, dead fluorescent tubes stayed black, but the path beneath his feet remained clearly defined. Every time his lead foot neared the edge of an illuminated zone, the next segment of baseboard flickered awake, drawing him deeper into the guts of the building. "It's tracking movement," Ryuki muttered, his voice raspy from thirst. "Or it's waiting for me." The air grew noticeably colder as he descended two flights of cracked concrete stairs. The stench of rain-washed ruin gave way to something crisp, dry, and clean—the distinct, artificial tang of closed-loop climate control systems. At the end of the lower hallway stood a single bulkhead door. Unlike the stripped steel and scorched drywall of the upper floor, this barrier was constructed from seamless black titano-alloy, brushed to a dull sheen. Stenciled across the center in gleaming chrome were two intersecting, razor-sharp letters: KC. --- Ryuki stopped three feet from the bulkhead. There was no keycard slider, no digital keypad, and no biometric thumbprint pad. As he stood before the silver emblem, a narrow horizontal slit above the frame clicked open. A line of intense red laser light shot out, sweeping down his body from head to toe. The beam paused on his right forearm for two long seconds. The red light flickered, turned a brilliant neon cyan, and snapped back into the wall. Heavy mechanical locks thudded inside the frame with the rhythmic crunch of tank gears. The large central disc on the door rotated ninety degrees counterclockwise, pulled back three inches with a hiss of released vacuum, and slid into the concrete wall. A burst of cold, purified air rushed outward, snapping the edge of Ryuki's cloak back. The air smelled of clean silicon, fresh oil, and pure ozone. He stepped across the threshold. The chamber inside was immaculate. Long, shadowless LED panels embedded in the ceiling lit every corner with blinding clarity. White marble floor tiles stretched to walls lined with recessed glass display vaults and high-density terminal racks. Nothing was broken. No layer of desert grit coated the consoles. The Zero Reverse had torn the surface world to pieces, but down here, thirty feet beneath the bedrock, time had simply stopped. In the center of the vault stood a heavy duel terminal mounted on a raised circular platform. Its interface plate was sleek dark metal, fitted with dual card-placement zones and a high-brightness holographic display hub. As Ryuki's foot struck the edge of the platform, the terminal's screen flashed to life. --- A synthetic voice, harsh and devoid of human inflection, vibrated from hidden wall speakers. "PRIMARY VAULT ACCESS DETECTED," the automated announcer declared. "KAIBA-CORP SECURE LOGISTICS NETWORK REQUIRES MANDATORY SYSTEM TESTING." The terminal's central deck tray slid open with a soft metallic click. Inside lay three unlabelled card decks, their edges glowing with faint blue standby indicator lights. "USER PROFILE: UNREGISTERED," the voice continued. "INITIATING AUTOMATED EVALUATION PROTOCOL KAIBA-001. DEFENSE ARTIFICIAL INTELLIGENCE UNITS COMING ONLINE." On the far side of the chamber, the floor plates split apart with a heavy hydraulic groaning. A metal pedestal rose six feet into the air. Atop it, a dense mass of holographic light coalesced into a humanoid shape—a tall, faceless combat mannequin framed in bright blue light. Its left arm bore an integrated hard-light duel disk, its card zones snapping outward with an iron *clack*. "PREPARE FOR SYSTEM EVALUATION," the AI commanded, its dual-ringed red optic sensors locking directly onto Ryuki. "LOAD DECK MODULE TO COMMENCE INTEGRITY TEST." Ryuki looked at the three glowing deck options on the terminal tray, then down at the worn deck of generic cards resting in his own belt pouch. A dry, cold smile touched his lips. Ryuki whispered to the empty room. "Just KaibaCorp tech and a test I don't intend to fail." He reached out and closed his fingers around the central deck module. --- Three hundred miles away, across the open sea in the high-tech heart of Neo Domino City, an alarm sounded inside an executive suite. The room was quiet, lit only by the ambient blue glow of floor-to-ceiling diagnostic monitors tracking the city's Momentum grid. Mokuba Kaiba sat at a broad desk of dark polished mahogany, reviewing operational reports for the city's upper sectors. He was in his early forties now, his dark hair trimmed neat at his shoulders, his suit tailored sharp to match the hard legacy of his family name. A harsh, rhythmic chime cut through the air. It was not coming from his main desk terminal. It came from an isolated console set inside a recessed wall panel behind his seat—a hardened, analog station connected to deep-underground landlines that had been dark for seventeen years. Mokuba paused. The pen in his hand froze over the signature line of a supply manifest. He stood up, his leather shoes sounding sharp against the polished hardwood floor. He walked to the corner, tapped his thumb against the biometric reader, and opened the dark glass panel door. The monitor inside was a monochrome green tube screen, flickering with erratic raster lines. Line after line of heavy block code streamed across the glass: ORIGIN: REGIONAL VAULT 01 - SUB-LEVEL 3 SIGNAL PROTOCOL: KAIBA-001 ACTIVE AUTOMATED DEFENSE SYSTEM: ENGAGED BIOMETRIC REGISTRATION MATCH: UNMATCHED / LEGACY AUTHORIZATION Mokuba gripped the edge of the metal frame, his knuckles turning white as his breath hitched in his throat. He stared at the pulsing ping on the green radar grid—a point located deep within the dead, abandoned ruins of the outer district. "Vault One..." Mokuba whispered into the empty office. "That system was destroyed during the Zero Reverse. The whole network was fried." He watched as the data lines refreshed, showing an active duel initiation code running through the vault's central processing matrix. "The defense AI is running," Mokuba said, his voice barely audible over the quiet hum of the room's air purifiers. "Who the hell just opened Seto's vault?"

Chapter 14: Vault's System Online