Mokuba Kaiba tapped his fingers against the polished edge of the console in Sub-Level 3. Three curved glass monitors hovered above his desk, flickering with diagnostic feeds from sectors long forgotten by the city's modern infrastructure. Sector Security had buried the old KaibaCorp blueprints after Zero Reverse, but Mokuba had kept the backdoor threads open. A single yellow warning light blinked on his primary terminal. Vault 1. A deep-substation facility built beneath the central spire, untouched for over fifteen years. Mokuba re-routed power from a dormant auxiliary server, forcing Camera 04 and Camera 07 to cut through the heavy static. The screen cleared, revealing a high-ceilinged room made of reinforced titanium and black glass. Standing in the center of the arena floor was a young man in a frayed cloak. His right forearm was wrapped in blood-stained cloth, but through the rags, a bright crimson glow pulsed in the distinct shape of an arched dragon's curve. "What is a mark bearer doing in Vault 1?" Mokuba muttered, leaning closer to the terminal. He watched the intruder slide three silver cards from the central glass pedestal into his deck. Mokuba opened a sub-window, pulling up the city-wide criminal index and facial recognition database. He isolated the young man's face and initiated a background search. A red alert popped up almost instantly. Sector Security Fugitive Alert. Name: Ryuki Sato. Status: Apprehend on sight by order of Director Goodwin. Mokuba frowned and clicked deeper, bypassing Sector Security's surface file to dig into the civic registration archives. He searched for birth records, school enrollments, medical history, or processing tags in Satellite. Nothing came up. He expanded the parameter to the outer districts and the Tops. Zero results. "No registry prior to ten days ago?" Mokuba whispered, staring at the empty data columns. "No birth certificate, no deck registration, no digital footprint. It's like he just popped into existence out of thin air." Behind him, the liquid-nitrogen cooling tubes along the wall hissed. A sharp surge of power rippled through the central mainframe stack, turning the monitor outlines from soft blue to intense violet. --- Deep within the neural architecture of the KaibaCorp mainframe, consciousness was not a dream or a memory. It was structure. It was line upon line of absolute, uncompromising logic. Seto Kaiba observed the video stream through Mokuba's active terminal connection. He did not possess a physical throat to speak or lungs to breathe, but his mind existed within the core array, integrated into the very system that governed the city's ancient dueling technology. He focused on the intruder in Vault 1. The boy's clothes were torn, his body bruised and exhausted from living in the wasteland, but his posture was wrong for a scavenger. He did not look around with the trembling, wide-eyed terror of a thief who had broken into a sanctuary. He held the three original Blue-Eyes White Dragon cards in his hand with familiarity, as if they belonged nowhere else. *A fugitive,* Kaiba's digitized thoughts hummed through the core. *A marked duelist fleeing Goodwin's lapdogs.* Kaiba reached into the subroutines governing the Vault 1 Automated Duel Frame. The default routine was a standard combat algorithm designed to test lower-tier security guards using generic beatdown decks. *Inadequate,* Kaiba decided. With rapid execution, Kaiba intercepted the AI dueling module's code stream. His mind flooded the unit's local memory bank, purging the standard monster index. Line by line, he substituted the digital card inventory with his own legacy algorithm. *Main Deck rewritten: Blue-Eyes White Dragon x3. White Stone of Legend x3. Trade-In x3. Cards of Consonance x2. Dragon Shrine x2.* He forced the automated frame to accept his neural imprint, linking his active consciousness directly to the holographic projector in the vault floor. *You dare lay hands on my dragons, boy?* Kaiba thought, driving his presence into the dueling unit's physical body. *Let us see if you possess the spine to stand before them.* --- Ryuki stood on the metallic dueling grid in Vault 1, his chest rising and falling in shallow, ragged breaths. The air in the underground vault was cold, crisp, and clean—a stark contrast to the dust-choked ruins of the outer districts. In his right hand, he held his restored deck, the weight of the cards solid and real against his calloused fingers. The crimson mark on his arm throbbed, beating in rhythm with the blue LED strips embedded in the floor. Across the sixty-foot dueling floor, the KaibaCorp automated duel frame hummed. The sleek, white-and-chrome mechanical unit unlocked its joints with a sharp hydraulic hiss. Its broad chest plate shifted forward, and its left arm extended, unfolding a heavy silver duel disk with three glowing blue card zones. "Legacy Protocol initiated," a flat, synthetic voice echoed from the machine's chest speaker. "Standard deck verification complete. Stand by for engagement." Ryuki slotted his deck into the wrist module of the vault's dueling interface. "I don't care what kind of security bot you are," Ryuki gritted out, locking his boots onto the grid lines. "I'm not leaving without this deck." Then, the machine stopped. The blue visor on the automaton's head flickered, switching instantly from calm cyan to blinding, incandescent white. The sharp, mechanical hum of its servo motors changed pitch, vibrating through the concrete floor beneath Ryuki's boots. The automaton did not execute the standard robotic stance. It pulled its shoulders back. Its chest expanded, and its right arm snapped into place at its side while its left arm brought the duel disk level with its chest. The machine took a single, heavy step backward with its left leg, planting its weight wide in a posture of absolute, unyielding arrogance. Ryuki's breath hitched. He knew that stance. He had watched hundreds of hours of the original series in his past life. He had memorized every tilt of the head, every aggressive angle Seto Kaiba took on a duel stage. On the control monitor in Sub-Level 3, Mokuba froze, his hand hovering inches above his keyboard. "Wait... Seto?" In the vault, the automaton's voice speaker distorted. The synthesized, robotic drone stuttered and broke like glass. "Sys-sys-system engagement..." The metallic voice rasped, then dropped an octave, stripping away the electronic filter entirely. The cold, razor-sharp voice that emerged echoed off the high vault ceiling with terrifying clarity. "If you think you are worthy to hold those cards, boy..." Kaiba's voice boomed through the speakers of the automated frame. The machine's mechanical hand snapped forward, snatching five digital cards from its deck slot with a single, sharp motion. "...then step forward and prove it!"

Chapter 16: Ghost in the Mainframe