The portal snapped shut behind them with a soft, almost polite pop—leaving only the hush of the forest.
They stood at the edge of a narrow dirt path that had once been a driveway. Ahead rose the Naberius estate: a three-story manor of dark stone and ivy-choked brick, windows boarded or broken, roof sagging under years of neglect. Three years since the murder. Three years since the Gremory cleanup squad declared the site "secured" and walked away. Nature had reclaimed most of it—moss crawling up walls, vines strangling the wrought-iron gate, weeds tall enough to brush Koneko's knees.
The air smelled of damp earth, rotting wood, and something faintly metallic that might have been old blood or just memory. Arto scanned the treeline once—slow, professional—then turned to Koneko. "You okay going in there?"
Koneko stared at the house for a long moment. Her nekoshou ears were still out, twitching at every forest sound, but her expression was calm—almost serene. "I'm not afraid," she said quietly. "This place… didn't hurt me. I was fed. I had a bed. I could sleep next to Kuroka-nee every night. That's all I remember here. The bad part… happened after."
Arto studied her another second—then nodded once. "Alright." He reached into void space and began equipping them with methodical efficiency. First: matte-black stealth suits—form-fitting, sound-dampening fabric that absorbed light rather than reflected it. Next: lightweight tactical masks covering nose and mouth, built-in filters and comms. Sound-canceling boots—soles that turned footsteps into whispers. Thin gloves—frictionless on the outside, fingerprint-proof on the inside.
For himself: a compact utility belt materialized—smoke bombs (three), flashbangs (two), a single matte-black combat knife sheathed at his lower back, and a suppressed short-barreled handgun holstered at his thigh.
Koneko declined weapons. She flexed her small hands—knuckles cracking faintly. "These are enough," she said simply. Arto didn't argue. Last—two layered spells. He raised his right hand—palm outward—toward Koneko first. A faint ripple of void mana washed over her: simple invisibility. Not true light-bending—too mana-intensive for long missions—but enough to blur their outlines, scatter attention, make eyes slide past them like water off oil.
Then the second layer. "Null Zone," he murmured. A second pulse—deeper, colder—settled over both of them like an invisible shroud. All ambient mana radiation ceased. No heat signature. No magical footprint. No detectable aura. Even high-end leyline scanners would read them as empty space.
Arto flexed his fingers—testing the field. Satisfied, he looked at Koneko. "Stay close. Move when I move. Stop when I stop. If anything feels off—anything at all—you tell me immediately. No heroics."
Koneko nodded once—sharp, certain. "Yes, Senpai." Arto pushed the rusted gate open—just enough for them to slip through. It didn't even squeak; the hinges had long since rusted into silence. They moved up the overgrown path—two ghosts in black—toward the front door of a house that had once been a laboratory, a prison, and a crime scene.
And somewhere inside—three years of dust, secrets, and unanswered questions waited. Arto placed one gloved hand on the doorknob. The door opened without resistance—almost invitingly. They stepped inside.
[Kunal's mansion]
Arto pushed the front door wider—slowly, hinges groaning in protest after three years of rust and disuse. A puff of stale, musty air escaped like a sigh from a long-sealed tomb. Dust motes danced in the thin shaft of late-afternoon light that followed them inside before the door clicked shut again, plunging the foyer back into near-darkness.
The house wasn't collapsing. Not yet. But it wasn't welcoming either.
Floorboards creaked under their weight with every careful step. Wallpaper peeled in long, curling strips like dead skin. A grandfather clock in the corner stood frozen at 3:47—whether AM or PM, no one would ever know. Cobwebs draped from the chandelier like gray lace. The air smelled of mildew, old paper, and something faintly chemical that lingered at the back of the throat.
Arto moved first—small, deliberate steps, boots silent on the warped parquet. His eyes had already shifted to night vision: pupils blown wide, pupils glowing faint violet as mana enhanced every photon. Koneko stayed half a pace behind and to his right—her own nekoshou senses sharp, ears swiveling at every creak and drip.
She didn't need night vision. This was her childhood home, even if only for a handful of years. The layout hadn't changed. Only the age had deepened. "Living room on the left," she whispered—voice flat, almost clinical. "Kitchen straight ahead. Stairs to the second floor on the right. Basement door under the staircase."
Arto nodded once—silent acknowledgment—and they moved. Living room first. Empty bookshelves lined two walls—shelves bare except for a few scattered medical journals with dates from fifteen years ago. A single armchair sat in the center of the room—upholstery torn, stuffing spilling like pale guts. No side tables. No pictures. No personal effects. Just… absence.
Koneko paused in the doorway. "There used to be a sofa here," she said quietly. "Kuroka-nee and I would sit together after dinner. She read to me sometimes. Old fairy tales." Her tail flicked once—restless. "Now it's gone." Arto didn't comment. Just filed the detail away. They continued.
[Timeskip: Brought to you by chibi Koneko lifting a bed and throws it at chibi Arto]
The master bedroom was the last room they checked. It looked like every other bedroom in the house—stripped bare, dust thick on the floorboards, a single broken window letting in pale gray light and the occasional rustle of wind through the ivy outside. The bed frame remained, though the mattress was long gone. Just a metal skeleton with a sagging headboard leaning against the wall like it had given up.
Arto stepped inside first—boots silent, senses extended. Then he stopped. Something was… off. Not a leyline scar. Not residual mana. Something subtler. A faint dissonance in the room's ambient flow, like a single wrong note in an otherwise silent symphony. His night-vision eyes narrowed. "There," he said—voice low, pointing at the headboard.
Koneko didn't ask questions. She moved to the bed frame, crouched, hooked her small hands under the metal rail, and lifted. The entire frame—easily two hundred kilos of iron and springs—came up like it weighed nothing. She pivoted smoothly and set it down against the opposite wall with barely a sound. Behind where the headboard had stood: a section of wall that didn't quite match the rest.
The plaster was slightly raised. The paint slightly newer. The seam almost—but not quite—invisible. Arto stepped forward—gloved hand running along the surface. "Illusion overlay," he murmured. "Thin. Amateurish by today's standards… but good enough three years ago." He pressed his palm flat.
A pulse of void mana—controlled, surgical—washed outward. The illusion shattered like cracked glass—revealing a metal door set flush into the wall. Dull steel. No handle. No keyhole. Just layers of deadbolt runes etched into the surface, all long since drained of power. Inactive. Locked. "The investigators were right—there was something hidden. Just not a full chamber."
He ran his hand along the edges again—measuring. "The wall thickness here is only twenty centimeters deeper than the rest of the house. Door's reinforced. This isn't a room. It's a compartment. A mailbox. A drop point. Or…"
He met Koneko's eyes. "…an entrance." Koneko's tails lashed once—sharp, decisive. She stepped forward. "Open it?" Arto moved aside. "Your Rook strength. Go." Koneko planted both feet. Knuckles cracked as she flexed her fingers. Then she drove both palms into the steel door—right at the center of the rune array. Metal screamed.
Locks—deadbolts, mana-seals, physical pins—snapped, shattered, crumpled under the sheer brute force of a Rook who had spent years under Arto's Abyssgard regimen. The door buckled inward like tinfoil, tearing free of its frame with a tortured groan.
Dust billowed. Koneko stepped back—breathing steady, ears twitching. The compartment behind the door was narrow—barely wide enough for one person to stand sideways. No deeper than a closet. No shelves. No furniture. Just a single wall panel—smooth concrete etched with the faint, ghostly outline of a magic circle.
Completely erased. Or so it appeared. Arto crouched—face inches from the wall—night vision piercing the gloom. "Sloppy," he muttered. "They scrubbed the surface runes. Burned out the active mana. But they didn't replace the wall. Didn't grind down the micro-traces. Repeated castings leave impressions—tiny, permanent echoes in the stone. Like grooves in a record."
He pressed his palm flat again—void mana flowing slow and cold. Faint violet lines began to glow—reconstructing themselves from the residual echoes. Stroke by stroke, curve by curve, the circle rebuilt itself in his mind's eye. "Teleportation gate," he said after a moment. "One-way outbound. Destination locked. Not a full portal—just a keyed exit. Probably set to a lab. An off-site facility. Somewhere Naberius could work without risking exposure in his own home."
Koneko's tails flicked. "Can you open it?" Arto studied the reforming circle—fingers tracing the air above it. "Not yet. It's keyed. Needs a specific mana signature or passphrase. But the traces are still here. Give me… five minutes. I can brute-force the echo reconstruction. Once I have the full pattern, I can forge a temporary key."
Koneko nodded—stepping back to give him space. Arto knelt—both hands now pressed to the wall—mana flowing in slow, precise pulses. The circle brightened—violet lines sharpening, runes reconnecting like a puzzle solving itself backward. Minutes ticked by. Dust settled. The forest outside stayed silent. Then—softly—Arto exhaled. "Got it."
He pulled his hands away. The circle pulsed once—faint, unstable, but alive. "One-use key," he said. "It'll burn out after we pass. Destination signature reads… deep. Underground. Heavy leyline density. Somewhere warded. Probably shielded from scrying." He looked at Koneko—dark-blue eyes steady. "We go through… we're committed. No turning back until we're on the other side. If it's trapped—if it's guarded—we fight. Or we die."
Koneko met his gaze—golden eyes fierce, unafraid. "I'm ready, Senpai."
[??? - Secret Facility]
Arto and Koneko stepped through the reconstructed circle in perfect silence—the portal's violet glow snapping shut behind them the instant their boots touched down on the other side. They emerged into pitch darkness. Not natural darkness. Engineered darkness.
The air was cold, dry, faintly metallic. No windows. No ambient light. Only the low hum of ventilation and the distant thrum of heavy machinery somewhere deeper in the complex. Arto's night vision kicked in immediately—pupils dilating to inhuman width, the world blooming into sharp monochrome greens and grays.
Koneko's own senses adjusted a heartbeat later—nekoshou eyes glowing faintly golden in the black. They were in a long, narrow corridor—bare concrete walls, reinforced steel floor plating, mana-suppression runes etched at regular intervals along the ceiling. High-security transit tunnel. Designed to funnel intruders into a kill zone.
And the kill zone was already active. Twelve guards—black tactical gear, balaclavas, suppressed rifles—stood in a staggered two-row formation thirty meters ahead, barrels trained exactly on the spot where the portal had just closed. Night-vision goggles down. Mana detectors clipped to chests. Finger discipline perfect—off the triggers, but ready.
The leader—a tall figure with silver rank pins on his collar—raised a gloved fist. "Portal signature confirmed," he barked into his throat mic. "Same harmonic as Naberius's old gate. Someone just used it. Again." A ripple of tension passed through the line. "Visual?" one guard asked—voice low, professional. "Negative. No heat, no mana bloom, no movement trace."
The leader's fist tightened. "Light them up." No hesitation. Twelve suppressed rifles barked in near-unison—subsonic rounds chewing concrete where the portal had been a second earlier. Sparks flew. Dust exploded. The corridor filled with the sharp thwip-thwip-thwip of silenced fire and the acrid stink of gunpowder.
Arto had already moved. He scooped Koneko under one arm—her small frame light as nothing—and dove left, rolling into the shadow of a support pillar. Bullets stitched the wall where they'd stood—high-velocity impacts cratering concrete, ricochet whining past their ears.
They pressed flat against the pillar—breathing shallow, bodies motionless. The barrage lasted eight seconds—disciplined, overlapping fields of fire—then ceased as abruptly as it began. Silence returned—broken only by spent casings tinkling to the floor. One guard lowered his rifle slightly. "Targets down?"
The leader shook his head—night-vision lenses glinting. "No body heat. No blood mist. No mana disruption. They're still here. Somewhere." He keyed his mic again—voice dropping to command level. "Control, this is Echo-1. Naberius gate reactivated. Unknown number of intruders. Zero visual, zero signature. Engaging with extreme prejudice. Request immediate lockdown and reinforcements."
A pause—static crackle—then a calm, distorted voice from the other end. "Lockdown authorized. Seal all sub-levels. Lethal force cleared. No prisoners. Higher-ups want this site sterile. Again." The leader nodded once. "Copy. Echo team—highest alert. Any sound, any step, any whisper—shoot to kill. No warning shots."
The guards spread out—two-by-two, sweeping sectors, rifles trained on every shadow, every corner. Arto—still pinning Koneko behind the pillar—kept his breathing shallow, Null Zone field holding steady. No mana leak. No heat signature. They were ghosts. Koneko's golden eyes met his in the dark—calm, focused, waiting for his lead.
He gave the smallest nod—stay low, stay silent—then tilted his head toward the far end of the corridor. A sealed blast door—red emergency lights pulsing faintly above it. Beyond it—whatever Naberius had hidden. Beyond it—answers. Arto eased forward—gloved hand on Koneko's shoulder guiding her in perfect sync.
Step by soundless step. Through the kill zone. Past the guards who would shoot anything that breathed. Toward the truth that had waited three years to be found.
[??? - Secret Facility - Main Hall]
Arto and Koneko emerged from the portal chamber into a vast, echoing corridor that immediately dwarfed anything they had expected.
The scale hit like a physical force.
The ceiling soared at least thirty meters high—brutalist concrete arches reinforced with mana-laced rebar, glowing faintly with embedded crimson runes. The corridor itself was wide enough to drive three trucks side by side; it stretched forward into vanishing perspective, side passages branching off every fifty meters like ribs on a colossal spine. Dim orange emergency lighting cast long shadows across the floor, punctuated by the harsh white glare of security floodlights sweeping in slow arcs.
This place wasn't just big.
It rivaled the full footprint of Arto's Simulation Room complex—multi-level, multi-sector, built for sustained high-volume experimentation. But where Arto's facility was sleek, precise, almost surgical in its design, this one felt… older. Cruder. Hungry. The walls were scarred with decades of mana burns, patched hastily with mismatched plates. Cables snaked across ceilings in thick, untidy bundles. The air carried the metallic bite of ozone and something far worse—fear-sweat, blood, charred flesh.
Koneko's ears flattened instantly. "Senpai…" she whispered through the comms bead in her ear. "The sigils on the walls. Those are Old Satan Faction marks. The original crest—before the new seal."
Arto's eyes flicked upward—night vision catching the faint, eroded runes carved into every support pillar: a jagged, six-winged star encircled by barbed chains. The symbol of the Old Satans. The faction that lost the Devil Civil War five hundred years ago. The war that placed Sirzechs, Serafall, Ajuka Beelzebub, and Falbium Asmodeus on the Four Great Satans' thrones.
He exhaled once—short, controlled. "Confirmed," he murmured back. "This is an Old Satan holdout. Buried. Forgotten. Or… deliberately kept alive." They moved. Small steps. Sound-canceling boots whispering against the floor. Null Zone cloaking their every emission. Invisibility spell bending light just enough to make them impossible to focus on. They were ghosts in a living fortress.
The corridor opened into the main hall—and the scale became oppressive. A cavernous atrium—easily five stories tall—ringed by catwalks and observation decks. Scientists in white coats and black tactical vests hurried between sectors, clipboards and tablets in hand. Armed guards—same black gear as the portal team—patrolled every level, rifles slung low but ready. Mana detectors swept the air in slow, methodical arcs.
And in every visible sector—glass-walled labs, reinforced containment chambers—experiments were in progress. Living experiments. Arto and Koneko paused in the shadow of a maintenance alcove, pressing against the wall. Through the nearest observation window:
A young birdgirl—barely older than Koneko had been three years ago—strapped to a tilted table. Tubes ran into her arms, her neck, her temples. Scientists in respirators adjusted dials while her body convulsed—silent screams behind soundproof glass, eyes wide with animal terror.
Another chamber: a succubus—virgin markings still visible on her lower back—suspended in a mana-drain field. Her skin was graying, lips cracked, eyes glassy as technicians drew vial after vial of glowing blood.
A third: human children—five, maybe six—wired to EEG arrays, tiny bodies jerking as low-level Senjutsu waveforms were forced through their meridians. One boy's horns were elongating against his will—minotaur traits being grafted by brute force.
Arto's jaw clenched so hard his teeth ached. He couldn't hear the screams. But he didn't need to. Every twitch. Every convulsion. Every tear-streaked face told the story. This wasn't innovation. This was vivisection for power. The exact opposite of everything he had built in the Simulation Room.
Arto's gloved hand clamped down on Koneko's shoulder—firm, unyielding, the pressure just short of painful. Her small body had gone rigid beside him, fist already rising, knuckles white, trembling with barely contained rage. Through the comm bead in her ear his voice came low, urgent, cutting straight through the horror. "Not now."
Koneko's head snapped toward him—golden eyes blazing, nekoshou ears pinned flat, fangs bared in a silent snarl. "They're screaming, Senpai," she hissed back over comms, voice shaking with fury. "They're alive. We can't just leave them like this. We have to—" Arto turned her fully toward him—both hands now on her shoulders, forcing her to meet his gaze through the tactical mask. His dark-blue eyes were calm. Cold. But not cruel.
"We will save them," he said—each word deliberate, carved into the silence between them. "All of them. Every single person in those tanks, every child they're breaking, every soul they've already used up. We save them all."
He leaned closer—forehead almost touching hers through the masks. "But if we move now—if we break one glass, kill one guard, trigger one alarm—they delete everything. Every file. Every sample. Every recording. Then they vanish. Relocate. Start again somewhere deeper, somewhere we'll never find. More victims. More screams. For years."
Koneko's breathing hitched—sharp, angry little gasps fogging the inside of her mask. Arto didn't flinch. "We need more than eyes on this," he continued. "We need proof. Undeniable. Ironclad. Data dumps. Specimen logs. Video archives. Names of the scientists. Names of the financiers. Names of whoever is still protecting this place after three years. We get that—all of that—then we bring the hammer. Gremory elite. Sitri strike teams. Sirzechs's royal guard if it comes to it. One coordinated strike. Total. Final. No escape. No second lab. No more victims."
He squeezed her shoulders once—gentle now. "But we only get one chance at that hammer blow. If we swing too early… we miss. And they keep going." Koneko's fist trembled in mid-air—then slowly, reluctantly, lowered. Her ears stayed flat. Her tails lashed once—sharp, frustrated—but she didn't pull away.
Arto held her gaze another heartbeat. "You're angry. Good. Hold onto it. Let it burn clean. But don't let it blind you. Not yet." Koneko swallowed—once, hard. Then nodded—small, jerky, but real. "…Yes, Senpai." Arto released her shoulders—gave one quick squeeze of reassurance. "We keep moving. We map every sector we can reach. We copy every file we can touch. We record everything. When we have enough… we call it in. And then we end this."
He turned back toward the corridor—gloved hand brushing her arm in silent stay with me. Koneko exhaled—shaky—then fell in step beside him again. Her voice came over comms—quiet, but no longer shaking. "When we come back… I want to be the one who opens every tank." Arto's scarred lips curved—just a fraction—behind his mask. "You'll be first through the door."
They moved on—two ghosts in black—slipping past patrols, past humming machinery, past glass walls filled with agony they could do nothing about yet.
[Timeskip: Brought to you by Koneko punching down a door into the screen]
Arto and Koneko pressed deeper into the facility, moving like shadows along the catwalks and corridors—past more glass-walled chambers, past more screams that never reached their ears but clawed at their hearts anyway.
The experiments weren't just biological anymore. They were weaponized.
In one sector, a restrained kitsune—three tails already severed and regrowing in agonizing cycles—was being forced to channel raw natural mana into a prototype mana-bomb. Every failed detonation scorched her fur black; every success drew clinical applause from the white-coated observers. In another, a young human boy—barely twelve—was strapped to a table while technicians injected him with distilled devil blood, watching his bones crack and reform in real time as they tested hybrid durability for frontline shock troops. The boy's screams were muffled by a sound-dampening field, but his eyes—wide, pleading, human—locked onto the glass for one terrible second before the next injection hit.
Koneko's breathing grew ragged beside him—small fists clenching and unclenching at her sides. Arto didn't speak. He didn't need to. They both understood: this wasn't science. This was torture dressed in lab coats. They kept moving.
Until they reached a sealed conference room—thick one-way glass, heavy soundproofing, red emergency lighting pulsing faintly above the door. Through the glass: eight figures seated around a long obsidian table. All male. All in white coats over tactical vests. All radiating the same cold, self-satisfied arrogance that came from believing themselves untouchable.
Arto placed a gloved palm against the wall beside the door—mana threading through the seams, disabling the alarm sensors without tripping them. The door unlocked with a soft click. They slipped inside. Invisible. Silent. Untraceable.
The lead scientist—tall, gaunt, silver hair slicked back, eyes hidden behind tinted lenses—leaned back in his chair at the head of the table, smiling the kind of smile that belonged on a predator watching prey bleed out.
"Progress reports," he said—voice smooth, cultured, utterly devoid of empathy. "Adaptability first." A younger scientist cleared his throat. "Subject group 14—kitsune lineage—shows 73% tolerance to the new hellfire derivative. Lethality threshold increased by 41% compared to baseline. We're ready for live deployment testing on low-threat targets."
The leader nodded—pleased. "Obedience metrics?" Another scientist—female, short-cropped black hair—tapped her tablet. "98% compliance in the latest batch after the third imprint cycle. The Naberius Protocol refinement is holding. Even when we push pain thresholds past 9.2 on the adjusted scale, they still obey. No resistance. No deviation."
Murmurs of approval around the table. The leader's smile widened. "Subject acquisition?" A heavy silence. The same woman answered—voice tight. "Slowing. Significantly. Gremory and Sitri have doubled patrols on leyline nodes. Youkai borders are tightening after the Kyoto stabilization breakthrough. We've lost three acquisition teams in the last month. We're down to secondary markets—human traffickers, rogue summoners—but the quality is dropping. We need high-potential stock if we want the Super Devil serum to reach viable combat thresholds."
The leader steepled his fingers. "Work harder," he said simply. "The higher-ups are impatient. Professor Naberius's dream—our dream—is within reach. An army of Super Devils. Unstoppable. Loyal. Perfect. No more groveling to the Four Satans. No more hiding in shadows. When we finish what Naberius started, the Underworld will kneel."
He leaned forward—smile turning razor-sharp. "Or burn." The meeting ended with a chorus of murmured agreements and chair legs scraping back. Arto—standing motionless in the corner—reached up and tapped the recorder bead behind his ear. The room was still for another heartbeat. Then Koneko's voice came through comms—small, trembling with barely contained fury. "Senpai...."
"I know, but we must go on." Arto answers firmly before they leave the room, and go deeper into the facility that is orchestrating the most twisted act of science Arto has ever seen.
Arto and Koneko pressed deeper into the labyrinth of corridors, each turn revealing horrors more grotesque than the last.
The deeper they went, the more the facility shed any pretense of "science." Glass chambers lined the walls like aquarium tanks—except the occupants were people. Living people. Strapped, suspended, wired, injected, dissected while still breathing. Some screamed silently behind soundproof barriers; others stared blankly at the ceiling, minds long broken, bodies kept alive only by machines that pumped nutrient slurry and pain suppressants in carefully calibrated doses. The lucky ones died quickly—thrown into industrial incinerators like medical waste, reduced to ash before their screams could fade. The unlucky ones lived. Endured. Were moved from one torment to the next—chemical burns, forced mutations, mana-overload experiments that lit their nerves on fire from the inside out.
Arto's jaw was locked so tight his teeth ached.
Koneko's breathing had turned shallow—short, angry little huffs through her mask. Her tails lashed behind her like whips, but she kept moving. Kept following. Kept recording.
They slipped past a chamber where a young dragon-kin girl—barely adolescent—was being vivisected alive, her scales peeled back layer by layer while technicians measured regeneration rates. Past another where human children were being force-fed diluted devil blood, bones cracking audibly as hybrid traits tried and failed to take root. Past a third where a succubus—virgin markings still visible—was being drained dry, her life force siphoned into glowing containment orbs while she begged—silently, endlessly—for it to stop.
Every room was worse. Every scream—though unheard—was felt. They reached the executive wing—offices now, not labs. Polished doors. Nameplates. The faint scent of expensive cologne trying (and failing) to mask the underlying reek of suffering. Arto stopped at the last door.
Dr. Shou Tucker - Director – Project Super Devil
He placed a gloved hand on the biometric scanner. Void mana flowed—subtle, surgical—overlaying his forged fingerprint and mana signature onto the system. The lock disengaged with a soft click. They slipped inside.
Tucker's office was pristine—dark wood desk, leather chair, floor-to-ceiling bookshelves lined with journals and specimen jars. A massive monitor dominated one wall, currently dark. No windows. No natural light. Just cold fluorescence and the hum of servers behind a hidden panel.
Arto moved to the desk—pulled the chair back—and sat. His fingers danced across the keyboard—void mana threading into the system like digital smoke. Firewalls crumbled. Encryption peeled away. Access granted. The screen woke up.
Files. Hundreds. Thousands. Project Super Devil Lead Researcher: Dr. Shou Tucker Original Framework: Prof. Kunal Naberius (deceased) Objective: Mass production of hybrid Super Devils—loyal, powerful, controllable—capable of overwhelming current Underworld military structures.
Sub-projects scrolled past:
Hybridization Protocols: Forced grafting of devil, fallen, youkai, and human traits onto base subjects. Success rate 4.7%. Obedience Imprinting: Refinement of Naberius's original potion. 98% compliance post-third cycle. Pain Threshold Enhancement: Subjects exposed to escalating torture to increase combat endurance. Current record: 47 days continuous stimulation without organ failure. Subject Acquisition Logs: 1,842 individuals (human, devil, youkai, fallen, angel hybrids) acquired over 3 years. 1,619 deceased. 223 active. 0 released.
Arto opened the file labeled Subject: Toujou Sisters – Log Archive.
Two sub-folders appeared.
Shirone Toujou: Empty. Not a single entry. No vitals. No test dates. No notes. Just a blank slate.
Kuroka Toujou: Hundreds of entries. Dates spanning nearly two years. Sessions logged with clinical precision.
Arto scrolled slowly—each line hitting like a hammer.
Session 47 – 3/12/XX: Subject Kuroka subjected to initial Naberius Protocol infusion. Emotional imprint established at 87% efficacy. Subject requested younger sibling (Shirone) be excluded from further trials. Request denied.
Session 112 – 7/19/XX: Pain threshold test #9. Subject exposed to sustained mana-overload for 14 hours. Subject repeatedly asked if Shirone would be next. Subject offered to double session duration if Shirone remained untouched. Request partially granted—Shirone moved to observation status only.
Session 189 – 11/4/XX: Hybridization attempt #3. Subject Kuroka injected with refined devil blood serum. Physical mutation successful—power increase 340%. Subject lost consciousness for 18 hours. Upon waking, first words: "Don't touch Shirone."
Session 241 – 2/28/XX: Super Devil evolution achieved. Subject Kuroka now exhibits stable Class-VI+ power output with full obedience lock. Final test scheduled: transfer protocol to secondary subject (Shirone Toujou).
Arto stopped scrolling. The final entry was timestamped the night of Naberius's death. Koneko—standing rigid beside him—had gone deathly still. Her breathing had turned shallow, ragged. Her small hands clenched into fists at her sides until her claws drew blood from her palms.
She read every word...Every date...Every plea...Every sacrifice. Her sister hadn't abandoned her. Her sister had protected her...Had taken every needle, every cut, every violation—so Shirone wouldn't have to...Had begged—again and again—for Kunal to leave the little sister alone...Had endured until the very moment Naberius planned to move on to Shirone...And then—only then—had she snapped.
Not in madness...In love...In protection.
Koneko's ears flattened completely. Her tails curled tight against her legs. A single, broken sound escaped her—half sob, half whisper. "Ne… nee-san…" Tears spilled—silent at first, then faster, tracking down her cheeks behind the mask. She reached out—small, trembling hand—touched the screen where Kuroka's final log glowed. "I… I hated you…" she choked out. "I was scared of you… I thought… I thought you wanted to eat me… I'm sorry… I'm so sorry, nee-san…"
Her voice cracked—small, childlike, lost. "I didn't know… I didn't know you were saving me… all this time… I'm sorry…" Arto moved before she could collapse. He pulled her into his arms—strong, steady—lifting her small frame against his chest so her face pressed into the crook of his neck. One gloved hand cradled the back of her head; the other wrapped around her shoulders, holding her tight enough to feel every shuddering breath.
She clung back—claws digging into his suit, tails wrapping around his waist like lifelines. Her crying was quiet—muffled against his chest—but devastating. Each sob tore something loose inside her—three years of fear, guilt, confusion, self-blame—all pouring out in hot, silent waves.
He just held her. Let her cry. Let her feel it all. Because some pain—after three years of silence—needs to be felt completely before it can begin to heal. He pressed his cheek to the top of her head—voice low, rough, meant only for her. "We'll find her," he whispered. "We'll bring her home. And when we do… you tell her yourself. Everything you just said. She'll hear it. She'll know."
Koneko nodded against his chest—small, broken, but real. She cried until her voice gave out again—reduced to soft, hiccupping breaths. When she finally quieted—exhausted, spent—Arto didn't let go. He simply held her.
Arto's fingers paused over the terminal keys. The screen had just finished loading the final encrypted sub-folder buried deep in the Naberius Archive – Sealed directory.
Project: Eternal BindLead Developer (Post-Naberius): Caesar Clown Primary Funding Source: Consolidated transfers from King faction shell companies (via layered proxies) Purpose: Mass production and refinement of the Naberius Protocol potion for commercial distribution to high-net-worth clients in the Underworld auction circuit. Revenue Allocation (redacted breakdown): 68% reinvested into Super Devil serum R&D; 19% facility maintenance and security; 13% personal accounts of senior staff (including current Director Shou Tucker).
Arto stared at the name. Caesar Clown. Not a myth. Not a ghost story whispered in succubus safe-houses. A real person. A real devil. The one who had taken Kunal Naberius's monstrous prototype and turned it into an industry. The one who had flooded the black market with the very potion that had chained generations of virgin succubi—turning love into a weapon, loyalty into slavery, choice into a privilege only the buyer possessed.
And the money trail led straight to the King faction houses. Shell companies. Blind trusts. "Consulting fees." "Research grants." Clean on paper. Filthy in reality. Every vial sold at auction, every soul broken by forced imprinting, every sister who had smiled adoringly at her abuser while her mind screamed—had helped pay for this.
For the tanks. For the children. For the vivisections. For the Super Devil serum that would one day flood the Underworld with obedient, unstoppable soldiers. Arto's scarred hand curled into a fist on the desk. Koneko—still standing beside him, small frame trembling with barely contained fury—looked up at his face. "Senpai…?"
He didn't answer immediately. Instead he plugged the data shard back into the terminal. Began copying. Everything. Every log. Every video. Every name. Every bank trail. Every memo that mentioned "King funding" or "Caesar Clown oversight" or "Super Devil viability threshold." The progress bar crept forward—slow, deliberate, unstoppable.
When it hit 100%, he ejected the shard, crushed it in his fist—mana flaring just enough to erase every trace of the copy from the system—and slipped the original (now carrying the only intact duplicate) into a void-sealed pocket.
Then he turned to Koneko. His voice was quiet—dangerously quiet. "We have it." Koneko's golden eyes searched his face. "All of it?"
"Everything," he said. "Proof of the potion's origin. Proof of Caesar Clown's involvement. Proof of King faction money flowing straight into this place. Proof of the Super Devil project. Proof of every subject—every child, every succubus, every species—who suffered here."
He exhaled—slow, controlled. "If this gets out—if Sirzechs, Serafall, Ajuka, and Falbium see this—the King houses will take a fatal blow. They'll deny everything, of course. Claim ignorance. Say the money was for 'legitimate research.' But the Rulers won't care about excuses. They'll see where the gold ended up. They'll see the tanks. The children. The dead. And they'll demand accountability."
Koneko's tails lashed once—sharp, angry. "Then we release it?" Arto shook his head. "Not yet." He looked back at the terminal—screen now wiped clean of their presence. "We don't release until we have the facility itself. Until we have physical proof that can't be denied—bodies, survivors, equipment, samples. Until we can prove this isn't just old records, but an active, ongoing atrocity. Then we drop everything at once. One strike. Total exposure. No deniability. No escape."
He met her gaze—dark-blue eyes burning with cold certainty. "I'm requesting Gremory and Sitri elite strike teams. If necessary—I'll ask Sirzechs for royal guard support. We take this place. We burn it to ash. We save everyone still breathing. And we end Caesar Clown's legacy here. Permanently." Koneko nodded
[Arto's mansion]
The portal snapped shut behind Arto and Koneko with a muted hiss, depositing them in the familiar foyer of the mansion just as the last violet light of sunset bled from the sky. Inside, the atmosphere was warm and alive—Radia's bright, lilting melody floated from the living room, the Hell Singer perched on the back of a sofa, tiny wings fluttering as she sang a cheerful nonsense tune about dancing stars and endless snacks.
The moment Arto stepped through the archway, Radia's song faltered.
Her small head cocked, crimson eyes locking onto his face. The joyful trill died mid-note. In its place came a slow, grim chord—low, resonant, almost mournful. The shift was instantaneous and unmistakable: a warning.
Every head in the living room turned.
Rias lowered her tablet. Akeno's teasing smile vanished. Nami's fingers froze on her phone. Grayfia set down the tea tray she had just lifted. Robin closed her book. Albedo rose from her seat without a word.
Arto walked forward—boots deliberate on the hardwood—until he stood in the center of the room, Koneko trailing half a step behind him. The little Rook's face was pale, eyes glassy, nekoshou ears drooping. Without preamble she scanned the room once—then launched herself straight at Nami.
Nami caught her instinctively—arms snapping around the smaller girl like steel bands. Koneko buried her face in Nami's shoulder, small hands fisting the back of Nami's shirt. Nami's protective-big-sister mode activated in under a second; she pulled Koneko fully into her lap, rocking her gently, one hand stroking down her back while whispering soft, soothing nonsense against her hair.
"Shh, baby cat… I've got you… you're safe… you're home…" Arto raised one hand—palm out—before anyone could speak. "Robin," he said—voice flat, carrying the weight of command. "Ward the house. Full lockdown. No leaks. Not a whisper gets out until I say so."
Robin was already moving—extra arms fanning out like a halo as she began tracing warding sigils in the air. Golden lines spread across walls, windows, floor, ceiling—sealing the mansion in layers of silence and secrecy. Arto pulled his comm device from his belt—thumbed it to conference mode—and opened encrypted channels to three recipients simultaneously.
Zeoticus Gremory
Sora Sitri
Sirzechs Lucifer
The holo-feed bloomed above the coffee table—three faces appearing in split screen. Zeoticus's warm, paternal smile disappeared the instant he saw Arto's expression. Sora Sitri's calm, analytical gaze sharpened. Sirzechs—already seated in his office—leaned forward, crimson eyes narrowing.
Arto didn't waste time on greetings. "I just returned from Kunal Naberius's abandoned estate," he began—voice low, clipped, every word carrying ice. "Koneko and I. We found the hidden sub-basement. We found the active facility beneath it. We found what Naberius started… and what Shou Tucker has continued for the last three years."
He paused—letting the names sink in. "Old Satan Faction holdout. Operational since before the Civil War. Never dismantled. Never discovered. Running full-scale experimentation on living subjects—devils, youkai, humans, fallen, angels, hybrids. Torture disguised as research. Weaponization of captured individuals. And at the center of it all: Project Super Devil. A continuation of Naberius's original work."
He tapped the data shard against his palm—once. "We have everything. Logs. Videos. Names. Funding trails. The potion that has chained virgin succubi for generations—its creator, after Naberius, is Caesar Clown. And the money that funded this place… traces directly back to shell companies controlled by multiple King faction houses. Whether they knew the exact nature of the expenditure or not… their gold paid for the tanks. The children. The screams. The bodies burned to ash."
Silence on every channel. Sirzechs's voice came first—quiet, lethal. "How deep does it go?" Arto met his gaze through the feed. "Deep enough that the Kings will take a mortal wound when this breaks. Deep enough that the Four Satans will have every justification they need to move. Deep enough that we cannot afford to wait. The facility is active. Right now. People are dying right now."
He looked down at Koneko—still curled in Nami's arms—then back up. "Koneko's sister, Kuroka Toujou, was one of Naberius's earliest subjects. She took everything—every injection, every cut, every violation—so Shirone would be spared. When Naberius planned to move on to the younger sister… Kuroka killed him. Staged her own 'madness' to draw hunters. Left Koneko where she would be found and protected. Took the blame. Disappeared. For three years."
Koneko made a small, broken sound against Nami's chest. Arto continued—voice never wavering. "We have proof. Undeniable. Video. Logs. Financials. Names. Enough to bury everyone involved. But we need to act fast. Before they realize the breach. Before they delete the evidence. Before they relocate and start again."
The projected screens flared with barely restrained fury.
Zeoticus's usually warm face was thunderous—eyes blazing crimson, strength already flickering at his fingertips, cracking the edge of his desk like dry earth under heat. Sora Sitri—normally the picture of composed calculation—had both hands flat on his table, the wood beneath them charring black as mana bled from his palms. Sirzechs sat perfectly still, but the air around him warped—ripples of raw destructive energy distorting the feed like heat haze over asphalt.
Rias stepped forward—fast—placing herself between the camera and her family's barely contained rage. "Father. Brother. Uncle Sora. Breathe." Her voice cut through the static like a blade—firm, commanding, the tone she used when peerages were on the verge of breaking formation. Zeoticus's fist unclenched—slowly. Sora exhaled through his nose—flames dying down to embers. Sirzechs blinked once—crimson fading to calmer red.
Rias didn't flinch. "We're angry. We're all angry. But if we act on rage alone, we risk them slipping away again. We do this clean. We do this right. We do this now." Arto stepped up beside her—still in his stealth suit, mask pulled down around his neck, expression carved from stone.
"I've already placed teleportation wards inside the facility," he said—voice level, carrying across all three feeds. "Exact coordinates locked. We know where it is. Naberius domain. Marquis Naberius clan territory. Deep underground, shielded, but not shielded from us anymore."
He looked straight into Sirzechs's eyes. "But we don't need an army for legitimacy. We need a royal decree. From you. Authorizing Gremory and Sitri as joint enforcers of the throne to breach and dismantle the site. Naberius can't resist. Can't retaliate. Can't claim sovereignty violation. Not when the order comes from Lucifer himself."
Sirzechs's gaze never wavered. "You have it," he said—voice like tempered steel. "By my authority as Lucifer, Gremory and Sitri are hereby deputized as royal enforcers. Breach. Secure. Extract survivors. Confiscate all data. Neutralize all resistance. No prisoners among senior staff. Full sanction. Effective immediately."
Zeoticus's voice followed—low, dangerous. "Gremory strike teams mobilizing now. Thirty elite. Full containment and extraction protocols." Sora Sitri nodded once—already tapping commands into his own console. "Sitri special forces en route. Twenty operators. Heavy suppression and medical evac support."
Arto inclined his head. "Thank you." He looked back at his family—gathered around him in the living room. "I lead this alone." Immediate protests.
Rias stepped forward—"Arto—" Akeno's wings flared—"Like hell—" Nami's voice cracked—"Boss, no—" Arto raised one hand—quieting them all. "Koneko has seen enough tonight," he said—soft but unyielding. "She stays here. With Nami. With you all."
He looked at Koneko—still curled in Nami's arms, eyes red-rimmed but steady. "You rest. You heal. You wait for us to bring your sister home." Koneko opened her mouth—then closed it. Nodded once—small, trusting. Arto's gaze moved to Rias. "You're needed here more than there. Koneko needs you. Akeno—same. Robin—coordinate from here. Keep the data flowing. Keep the wards up. Keep everyone safe." Rias's jaw tightened—but she nodded.
Akeno's wings folded slowly—reluctant but accepting. Robin simply inclined her head. Arto looked at Nami last—knowing exactly what she wanted to say. She hugged Koneko tighter instead of arguing. "Bring them all back, boss," she whispered. "Every last one."
Arto nodded once. "I will." He turned to Albedo—stepped close—cupped her face with both scarred hands. "Stay with them," he said quietly. "Keep the house standing." Albedo pressed her forehead to his—ring glinting between them. "Come back whole," she whispered. "That's all I ask."
Arto kissed her—brief, fierce, grounding—then stepped back. He looked at Grayfia. "Hold the fort." Grayfia bowed—small, perfect. "As you command, Master."
[Timeskip: Brought to you by Arto walking across a readied army]
The staging ground was a shadowed clearing deep in neutral territory—far enough from Naberius lands to avoid early detection, close enough for the strike to be surgical and swift. Portable mana-dampeners hummed low, cloaking the entire force from casual scrying. Seventy souls stood in disciplined silence: thirty Gremory elites in crimson-trimmed black tactical armor, twenty Sitri special operators in deep indigo, and twenty royal taskforce members bearing the four-winged Lucifer-Leviathan seal on their pauldrons—Sirzechs and Serafall's personal enforcers, authorized to act with full throne legitimacy.
Arto stood before them—mask down, scarred face lit by the faint violet glow of the tactical holo-map projected from his palm. The facility schematic rotated slowly in mid-air: every corridor, every lab, every containment chamber, every guard post marked in precise overlays. Red dots pulsed where he had already seeded the kill-switch viruses. Blue lines traced the teleportation wards he had embedded during the recon—silent, one-way gates ready to open on his command.
He spoke once—voice low, calm, carrying to every ear without raising. "No mistakes." He tapped the map. It zoomed to the main atrium. "Four objectives. Equal priority. No hierarchy."
- Secure the data "Primary servers are in sub-level 3, central core. Viruses are already in place—they'll lock out deletion commands and begin exfiltration the moment we breach. Robin will handle remote mirror-copy from the mansion. Your job is physical security: reach the core, hold it, let the data flow. Do not let them pull physical drives or trigger local wipes."
- Capture the culprits "Senior scientists—Shou Tucker chief among them—must be taken alive. Memory extraction is mandatory. Guards and junior staff are secondary; lethal force authorized if they resist. No scientist walks out breathing unless restrained."
- Suppress resistance "Expect heavy security—Old Satan holdout veterans, enhanced hybrids, automated turrets. Neutralize immediately. No quarter for anyone who fires first. Royal decree covers full lethal authorization."
- Save the subjects "Primary mission. Every living being in those tanks, cages, and restraints comes out. Medical evac teams are pre-staged on the other side of the portals. Prioritize children and high-value captives—succubi, any marked subjects. No one left behind. No one forgotten."
He tapped again. The map pulsed red at four entry points—his pre-placed wards. "We strike simultaneously. Four teams. Gremory takes north and east. Sitri south and west. Royal taskforce follows me through the central breach—I'll open the primary gate. We go in hard, fast, quiet until resistance forces our hand. Once the alarm sounds, it's total war."
He looked up—meeting every gaze in turn. "Scientists live. Guards die if they resist. Subjects come home. Data comes with us. This facility ends tonight. No second lab. No second chance for these people." A ripple passed through the ranks—silent, resolute nods. Arto raised his hand—palm outward. "Royal decree is active. Gremory and Sitri act under Lucifer-Leviathan authority. Naberius has no legal standing to resist. If they try… they become complicit."
He closed his fist. "Move to breach positions." The force dispersed—silent, practiced—vanishing into shadow and mana-cloaks toward their assigned vectors.
[Naberius Domain - Hidden Facility]
The alert siren tore through the facility like a wounded animal—red emergency lights strobing across every corridor, every lab, every cage. A calm, automated voice began repeating overhead: "Intrusion detected. All sectors to lockdown. Purge protocols initiated. Data deletion commencing in sixty seconds."
It never got to thirty. The breach was surgical. Merciless. Total.
Gremory strike teams materialized first—crimson-armored shadows pouring through Arto's pre-placed teleportation wards. Sitri operators followed in indigo waves—silent, precise, already sweeping sectors with suppression fields that choked mana signatures and jammed comms. The royal taskforce brought up the rear—twenty black-clad figures bearing the four-winged Lucifer-Leviathan seal—moving with the absolute authority of a throne decree. No hesitation. No negotiation. Only execution.
Guards died in seconds. The first patrol—eight men—never even raised their rifles before Gremory blades found throats and Sitri lightning cores detonated inside their armor. A second squad tried to fall back to a choke point—only to walk straight into a royal taskforce kill-box: synchronized Power of Destruction pulses that turned the corridor into a crematorium. No screams. No second chances. Just ash drifting across the floor.
Data core room—sub-level 3. A frantic technician slammed his palm on the master purge console—screen flashing DELETION 87%—when a Gremory operative's blade punched through his spine. Another scientist tried to yank physical drives from the racks—Sitri ice encased his arms mid-motion, freezing flesh to metal. The drives were ripped free, sealed in mana-locked cases, and passed to the extraction team before the purge could finish.
DELETION ABORTED – EXTERNAL OVERRIDE
Robin's voice—calm, distant—came through Arto's comm. "Data secured. Full mirror copy complete. No wipe was successful." Shou Tucker never made it out of his office.
He was still smiling—still believing himself untouchable—when the royal taskforce breached the door. Two operatives moved faster than thought; one pinned his arms with null-mana cuffs, the other slammed a neural suppressor collar around his throat before he could speak a single word. Tucker's smile vanished—replaced by wide-eyed panic—as he was dragged out, still alive, still conscious, still destined for memory extraction.
Caesar Clown almost escaped. He dissolved into smoke—gray tendrils coiling toward a hidden vent—only for a Sitri suppression field to snap shut around him like a vice. The smoke recoiled, reformed, solidified. Caesar hit the floor on his knees—gasping, choking—while indigo-armored operators clamped void-forged restraints around his wrists and ankles.
"Target secured," the Sitri squad leader reported. "Caesar Clown in custody. Alive." Arto didn't hear the confirmations. He was already moving—leading the Gremory extraction team through the deepest sub-levels, past labs now swarming with allied forces shutting down machines, cutting power, freeing restraints.
And then they reached the holding bays. The scale hit like a physical blow. Not hundreds. Thousands.
Cages stacked floor to ceiling—row after row after row—each one containing a living being. Humans. Devils. Youkai. Fallen. Angels. Hybrids. Children. Elders. Some still conscious—reaching through bars with trembling hands, mouths moving in silent pleas. Some convulsing—bodies warped by forced mutations, chemicals burning through veins. Some already still—eyes open, vacant, waiting for death to finish what the scientists started.
The smell hit next—blood, sweat, vomit, charred flesh, fear. Even the most seasoned Gremory veterans faltered—rifles dipping, breaths catching. One soldier—a grizzled sergeant with twenty years of service—choked out a single word. "…How many more?" Arto didn't answer.
He couldn't. He just moved—fast, methodical—tearing open the first cage with void-enhanced strength. The occupant—a young catgirl, ribs visible, one ear half-missing—collapsed into his arms. He passed her to the nearest medic without a word—then moved to the next cage. And the next. And the next.
"Priority evac!" he barked over comms. "All teams—drop everything else. Subjects first. Get them out. Get them out now!"
Medics flooded in—portable stretchers, mana-stabilizers, emergency IVs. Portals snapped open—dozens at once—leading straight to field hospitals pre-staged on the surface. Survivors were carried, dragged, levitated—some weeping, some silent, some too broken to react at all.
A Sitri medic knelt beside a dying dragon-kin boy—barely breathing—then looked up at Arto with haunted eyes. "They said they needed more… they kept saying they needed more…" Arto didn't reply. He just kept moving—cage after cage—until his hands were slick with blood not his own.
Until the screams—heard or unheard—echoed in his skull. Until the facility—once a fortress of cruelty—was being torn apart from the inside by people who refused to let it stand another hour.