The facility lay deep in the Underworld.
Not in a palace of black marble and stained glass.
Not at the top of a dramatic tower silhouetted against crimson skies.
It was a low, quiet medical complex carved into the side of a basalt hillside, its exterior plain enough that most devils would walk past without a second glance. The only hints were the layers of wards—so dense that even most Maou would have bounced off if they tried to force their way in.
Sona had never been here.
Serafall had, once, a long time ago.
Ajuka led them through sterile corridors of white stone and polished black tiles, his aura hovering just above the ward-lines, nudging the arrays aside with casual ease. Where his presence passed, complex sigils folded open like mechanical irises and then sealed shut again behind them.
Ren walked a half-step behind, hands in his pockets, posture loose.
Sona walked beside him, spine straight, fingers clenched around the folder she wasn't actually reading.
Serafall's usual glittering aura was muted, her steps quiet, eyes sharper than anyone in the hallway had ever seen on the so-called Magical Girl Maou.
They passed research rooms and containment wards. Behind some of the doors, Sona caught glimpses of other patients—devils suspended in stasis-fields, magic circles pulsing rhythmically; monitors displaying brainwaves, demonic power fluctuations, and unfamiliar parameters that made even her scholar's instincts flinch.
But they didn't stop.
Ajuka didn't slow until they reached a heavy door with no handle, just a smooth obsidian surface etched with a lattice of faintly glowing lines.
Two devil researchers stood on either side, white coats crisp, expressions weary. Their eyes widened when they registered Serafall and Sona.
"Maou-sama—!"
The female researcher almost tripped over her own bow.
"At ease," Serafall said, voice softer than usual but stripped of her normal sing-song. "We're here to visit a patient."
Her smile didn't reach her eyes.
Ren stepped forward.
The door responded not to him, but to Ajuka. The green-haired Maou's aura brushed the surface; seals peeled back with a soft, mechanical sigh as the locking mechanism recognized the signature of its creator.
"Record everything," Ajuka said quietly to the researchers. "No interference unless I say so."
They nodded quickly.
The door slid aside.
Inside, the room was quiet.
White walls.
Soft lighting.
A single bed, surrounded by unobtrusive medical equipment and a few floating magic circles that monitored things no human machine could: demonic power loops, Sacred Gear activity, sleep-depth patterns only Ajuka's code could interpret.
On the bed lay a girl.
Long violet hair spilled over the pillow in waves.
Her face looked young—late teens, maybe. Fine-boned, almost fragile. Her eyes were closed, lashes long against pale skin with that faint, translucent quality Sona had seen in long-term patients before. A simple hospital gown, blankets drawn neatly up to her chest, IV lines threaded into the crook of her arm.
She could have been a student sitting in a classroom.
She could have been walking down a seaside street, laughing with friends.
Instead, she looked like someone who had been sleeping far, far too long.
Sona's throat went tight.
Serafall's hands clenched into fists at her sides, knuckles white.
Ajuka stood at the foot of the bed, eyes flicking between the monitors and Ren, watching the way the cultivator's aura shifted as he took in the scene.
"This is Ingvild," Ajuka said. "Ingvild Leviathan. Half-human descendant of the original Leviathan. Patient of the Sleep Disease for… one hundred and three years, subjective time."
Sona exhaled slowly. The theory, the rumors, the scattered research papers she'd read all came crashing together with a name and a face.
The Sleep Disease.
A devil-specific condition that sent its victims into a deep sleep they couldn't wake from. Their bodies weakened, their power decayed, and eventually they died unless kept alive artificially. For a century, devil doctors had tried everything: magic, potions, demonic technology, Ajuka's code itself. No one had found a consistent cure.
"A unique case," Ajuka went on, voice turning clinical. "Her body is currently stable under artificial support. The disease itself… has resisted all known interventions. There are external complications—her dormant Sacred Gear evolved while she slept, its logic intertwining with the pathology."
He glanced at Ren.
"In other words," he said, "the knot is tight."
Ren didn't answer.
He stepped closer, every hint of casualness smoothing out into focus. The warm, easy-going cadence in his voice had receded, leaving behind the quiet concentration Sona had come to associate with him doing something truly important.
He reached out.
Placed his fingertips gently on Ingvild's forehead.
At the same time, his other hand rose, two fingers touching the space between his brows—where, if someone had eyes for it, they would see a phantom white-gold spine etched into existence, patterned with Dao-lines from another universe altogether.
The Immortal Soul Bone thrummed.
To everyone else in the room, nothing visible happened.
To Ren, the world shifted.
Her soul opened like a book he'd been waiting to read.
The disease indeed wasn't just an "illness."
It was a knot.
Threads of demonic power, human bloodline, and Sacred Gear logic tangled together, wrapped around her consciousness like a cocoon—and a chain. Each time her power tried to naturally awaken, the knot tightened, forcing her deeper into sleep to keep the system from tearing itself apart.
"Messy," he murmured under his breath.
Sona heard the word and shivered. She couldn't see what he saw, but the faint change in his tone told her enough.
Ren closed his eyes.
His Heaven opened.
Twelve Fate Palaces turned behind him—not outwardly, but in the quiet space between breaths and heartbeats, stacked like twelve worlds inside his soul. Dao-characters flared across their surfaces, each one a law, a principle drawn from Nine Worlds, Tenth World, Three Immortals, Eight Desolates.
In this world, no one knew the language those symbols spoke.
He extended a thread of his Dao through the Immortal Soul Bone, down his arm, into Ingvild's soul.
The knot resisted.
It was old.
Stubborn.
Born from fear and the Underworld's attempt to handle something it didn't understand—a hybrid body, a budding Longinus whose song could command dragons and the sea, an incurable disease devils whispered about in research circles and then tried not to think about.
"I know," he thought at it. "You did your best."
He didn't attack it.
He didn't brute-force a path through.
He labeled.
The Immortal Soul Bone took the complexity and made it simple.
This thread: a virus-like pattern eating at neural pathways, a Sleep Disease loop that amplified itself every time her brain tried to reach wakefulness.
This one: Sacred Gear auto-defense logic, wrapping around the virus to keep it from spreading too fast, changing its shape whenever something tried to pry it loose.
This one: Underworld ambient laws reacting to a half-human, half-devil body, pushing her toward neat categorization and failing—creating stress fractures in her Anima.
This one: Ingvild's own soul-light, her Anima, flickering weakly at the center, trying to shield itself with the faint instinct of someone who hadn't even had the chance to grow up.
Ren smiled, internally.
"Found you."
He stepped inward.
...
The world changed.
He stood on a shore.
Not any shore he knew, but one that felt like a memory someone had wrapped in music and tucked away.
The sea was calm, stretching to the horizon, colored in deep indigo and violet. The surface shimmered with soft, aurora-like hues, each wave cresting in pale luminescence before dissolving into the next.
Above, the sky was starless—but not dark. A deep, gentle twilight arched overhead, painted in gradations of purple and blue that never quite settled into night.
Waves lapped at the sand in a slow, steady rhythm.
He realized, after a moment, that they moved in time with a melody he couldn't quite hear—like a song humming just out of range.
On the water's edge, a girl sat with her knees drawn up to her chest.
Violet hair moved in the breeze, catching flickers of sea-light.
Her dress was simple and white, bare feet half-buried in the sand, toes pressed into the cool surface.
She hummed something under her breath, a tune so soft it almost fused with the sound of the waves—but every note shaped the air around her, drawing threads of sea and sky into a gentle spiral.
When he stepped closer, she turned.
Her eyes were a soft, muted red. Not sharp, not fierce—just tired and clear.
They widened when they saw him.
"…Ah," she said quietly. "Another dream?"
Her voice held that strange mixture of hope and resignation that only came with long solitude.
Ren smiled and dropped easily into his usual drawl.
"Something like that," he said. "Mind if I sit?"
She blinked at him, surprised at the casual tone.
Then, after a moment's hesitation, she nodded.
He sat beside her, folding his legs, letting the water wash up to his ankles. The sand felt cool, the kind of cool you only got at night on a beach when the sun had been gone for hours.
They didn't speak at first.
Waves and her quiet humming filled the space between them.
The melody circled back on itself, sometimes slipping into a minor key, sometimes brightening, as if her mood kept brushing the notes without deciding where to rest.
Finally, she broke the silence.
"You feel… different," she said slowly. "Most of the dreams are fuzzy. Or… faint. They don't look at me."
"I'm very nosy," he said mildly. "I like looking at people."
She gave a tiny, self-conscious smile, fingers tightening slightly on the hem of her dress.
"That sounds… a little scary," she said.
He chuckled.
"Only for my enemies," he replied. "For cute girls, I'm very gentle."
Color bloomed across her cheeks, a faint blush against pale skin.
"…Cute," she echoed under her breath, like she was tasting the word. "I'm… just sleeping."
"You've been sleeping a long time, Ingvild," he said.
She stiffened.
Turned fully toward him.
"…You know my name," she whispered.
"Of course," he said, voice softening. "Ingvild Leviathan. Half-human descendant of the original Leviathan. The girl whose song scared grown devils so much they decided to hide you instead of dealing with their fear properly."
Her fingers dug into the fabric of her dress.
"That's… a harsh way to put it," she said, her tone a little shaky.
"It's accurate," he said simply. "And none of it is your fault."
Her gaze dropped to the sand.
He let the waves wash up, recede, wash up again. The dreamsea's rhythm synced with her breathing.
"…If I wake up," she said slowly, "I'll be trouble."
The words came out flat, like she'd rehearsed them a hundred times in empty dreams.
"People said my power was… dangerous. That if I sang, I might… control them. Or hurt them. Or…"
She trailed off, throat closing around the rest.
Ren watched her profile, the way her eyes tightened on the horizon.
"You're worried you'll be a weapon," he said quietly. "Instead of a person."
Her shoulders trembled.
"Yes," she whispered. "If I stay asleep, at least… I'm not hurting anyone. I'm not… in the way."
He let the silence breathe for a moment.
"You know," he said, "there's a woman I know who thought something similar. Big power, ugly history, a reputation that made people whisper. She could've stayed distant. Instead, she learned to laugh anyway. Now she uses her ice to protect kids."
Lavinia's quiet, distant smile flashed through his mind, Absolute Demise humming like a winter sun.
"There's another who carries curses in her chest," he went on. "She thought she was just a walking disaster. Now she uses that hunger to eat evil instead of innocent hearts."
Shigune, cradling her mug of cocoa, came next.
"And there's a kid with a dragon in his arm," he added, lips twitching. "He thought he was just a punching bag for the strong. Now even gods flinch when he gets serious."
Issei, yelling something ridiculous about harems and justice while punching Satan-class enemies in the face.
Ingvild listened, eyes wide, the melody she'd been humming fading away entirely.
"You…" she said slowly. "You help people like that?"
"Sometimes," he said. "Sometimes I just give them a push and they do the rest. Sometimes I do more."
He turned fully toward her.
"Right now," he said, "I'm here for you."
She swallowed, throat working.
"I don't even know you," she whispered.
"You will," he said. "Name's Ren."
He offered his hand, palm up, fingers relaxed.
"Nice to finally meet you."
She stared at his hand like it was some dangerous relic.
Then, very slowly, she slid her own hand into his.
His grip was warm.
Steady.
"…Why?" she asked. "Why me?"
He smiled.
"Because you're cute," he said easily. "Because you were punished for existing. Because your song deserves to be heard because you choose to sing it, not because somebody pushes you to."
Her eyes filled, just a little.
"You say that so easily," she murmured. "Like it's… simple."
"I'm very good at telling the truth," he said. "Makes life simpler, actually."
He squeezed her hand gently.
"I'm going to untangle the knot you're stuck in," he said. "The disease. The Sacred Gear's overprotective panic. The fear other people wrapped around you. I'm going to give your power a cleaner spine. Make it so when you sing, you aren't burning yourself just to keep the world 'safe.'"
Her breath hitched.
"Can you… really?" she asked. "Everyone said…"
"I've been doing 'impossible' since I landed in this world," he said, voice going calm, matter-of-fact. "Your case is delicate. But not impossible."
"And if something goes wrong?" she whispered. "If your power… breaks something? If I…"
"I'll take the hit," he said, without even a heartbeat of hesitation. "Your soul's already exhausted from holding this pattern together. Let me carry it for a while."
She looked at him like he'd just offered to hold up the sky.
"…You're strange," she whispered.
"I get that a lot," he said, amused. "I also keep my promises."
He lifted their joined hands.
Pressed the back of hers lightly to his lips.
"Ingvild," he said, voice dropping a shade lower. "I'm going to wake you up. Not because the world needs your power. Because I want you to see the sky. Eat food that isn't fed through a spell. Complain about the weather. Maybe sing just because you feel like it."
Tears slipped down her cheeks.
She let out a brittle little laugh that turned warmer halfway through.
"You're… very smooth," she said.
"Is it working?" he asked.
She hesitated.
Then nodded, a small, helpless motion.
"…Yes," she admitted.
"Good," he said softly. "Then trust me. Just a little."
She took a shuddering breath.
Closed her eyes.
"…Okay," she whispered. "I'll… leave it to you, Ren."
He smiled, that easy, relaxed curve of lips that had disarmed devils and gods alike.
"Good girl," he said quietly.
He let go of her hand.
The dreamsea trembled.
Lines of Dao-light rose from the water, spiraling up around her like gentle, glowing vines—extensions of his Fate Palaces reaching into her inner world.
She didn't flinch.
Didn't fight.
She let go.
Everything else was his work.
...
In the physical room, only a heartbeat had passed.
Sona watched Ren stand very still, one hand on Ingvild's forehead, the other touching his own brow where the Immortal Soul Bone resonated. His aura was subdued, coiled inward, but the weight of it made even the reinforced medical equipment vibrate faintly.
Serafall chewed her lower lip, hands clasped so tightly in front of her that her fingers trembled.
Ajuka's eyes flicked over the readouts hovering above Ingvild's bed. Magic circles spun faster as values shifted.
"Her brain activity is spiking," one of the researchers breathed. "Sh-should we—"
"Do nothing," Ajuka said sharply, never looking away from the data. "You move, you interfere, you'll die before you understand how."
The researcher swallowed audibly and stepped back.
Ajuka's eyes narrowed.
Ingvild's neural patterns, demonic power circuits, Sacred Gear signatures—everything that had been flat or circular for decades—suddenly surged. Peaks formed where there had only been plateaus. Harmful feedback loops that once reinforced the Sleep Disease began to misfire, data points stuttering like something was cutting in between them.
"…Incredible," he muttered. "He's… introducing an external lawset directly into her soul. The system should be rejecting it. But it's… not."
His voice dropped into something like awe.
"It's adjusting."
...
Inside Ingvild's soul, the surgery felt like a battle.
Ren moved like a surgeon and an architect—and like a cultivator used to bending entire worlds.
He followed the disease-thread first.
It tried to lash at him—tiny, virus-like sigils snapping toward his invading Dao, trying to infect, to copy, to spread. Every time it sensed something foreign, it tried to wrap around it, drag it into the same sleep-loop.
Ren's Fate Palaces turned once.
Lines of Dao-essence extended like needles of light. They didn't cut the disease; they pinned its behavior in place long enough for the Immortal Soul Bone to read it.
He isolated each loop.
Slipped tiny fragments of his Dao essence around them, threading them like beads on a string.
Vicious, self-reinforcing cycles became sealed circuits—closed loops that would feed on their own energy until they burned themselves out without touching her core.
The Sleep Disease screamed in silence, trying to adapt.
It had learned over a century. It had reshaped itself every time devil doctors infused medicines, injected spells, attached machines. It had survived Ajuka's early experiments by mutating around his code.
Ren's Dao didn't give it the time.
His Immortal Soul Bone turned complexity into simplicity. Patterns that had taken years to evolve were broken down into clean equations. The disease shifted once, twice—and each change was recorded, filed, and sealed into its own tiny, harmless ring.
"Your trick is adaptation," he thought calmly. "Mine is understanding."
Next, he traced the Sacred Gear's connection.
Nereid Kyrie's logic pulsed like a heartbeat buried deep under the sea. It tasted of tides and storms, of dragons coiling in the depths. The auto-protection routines had been active from the start, trying to keep the disease from killing its host by forcing her deeper and deeper into sleep.
Self-defense had become suffocation.
Ren followed the chains of logic—points where the Sacred Gear rerouted stress back into Ingvild's soul, pressure valves that never opened—and slowly rerouted them.
He drew the pressure away.
Through himself.
Through his own Heaven.
He pulled the wild, overprotective loops into the neutral chaos layer between his Fate Palaces—an artificial buffer forged from refined primordial energy and Myriad Origin's closed-loop efficiency. There, Nereid Kyrie's protective algorithms could run as much as they wanted without crushing the girl they were meant to save.
The Sacred Gear bucked once.
Power surged, and for an instant the dreamsea roared. Phantom dragons of sea-light rose from the waves and lunged at him, eyes glowing with the mindless instinct of a system that had never learned the difference between ally and invader.
Ren's Dao flared.
Hell Suppressing Immortal Physique settled under everything like a hidden mountain range, an unyielding foundation that made the entire inner world feel heavier. The dragons hesitated, the water itself slowing as his authority pressed down.
"Easy," he murmured, even here, even now. "I'm not here to break you. Just to teach you where not to bite."
He reshaped the chains.
Instead of feeding stress into Ingvild's Anima, he rerouted it into a circuit connected to his own Heaven—and to the Myriad Origin loops tucked into her newly-stabilized Soul Palace pattern. What once had been crushing pressure became fuel for a stronger, cleaner circulation.
Finally, he reached her Anima.
Small.
Stubborn.
Wrapped around itself like a seed under too-heavy soil.
He didn't tear the soil away.
He brushed it.
A gentle touch of Dao-essence, not his full weight—just enough to let her feel that there was something else holding up the sky.
"Wake up slowly," he told it. "You don't have to carry this alone anymore."
The Immortal Soul Bone sang.
Complexity became simplicity.
The knot loosened.
Unwound.
Reworked into a cleaner pattern—a braid instead of a tangle, threads of devil blood, human heart, Longinus song, and his alien Dao woven into something that could actually breathe.
...
Outside, the monitors went wild.
Magic circles flared, then smoothed, patterns rearranging themselves. Non-linear graphs that had once looked like heartbeats flatlining suddenly resolved into healthy, rhythmic lines.
Ajuka's lips parted.
"…Impossible," he whispered. "Disease markers—dropping. Sacred Gear activity—stabilizing. Magic circuits—re-harmonizing. There's… no backlash. No systemic rejection."
One of the researchers choked.
"That's… that's cleaner than any artificial Sacred Gear integration we've ever managed," he stammered.
Ajuka ignored him.
His entire focus was on the data—incomplete, yes, because even his Demonic Code couldn't read the foreign lawset Ren was using—but enough to hint at what was happening.
"He's not just suppressing it," Ajuka murmured. "He's reworking the underlying behavior."
Serafall's eyes were wet now, but her lips were set.
"Come on, Ren-chii," she whispered. "Save the princess…"
Sona said nothing.
Her hands trembled.
Deep in her own Soul Palace, her Anima leaned forward, the Throne of her carefully-built self watching this alien Dao brush against the boundaries of what she understood.
A Maou of the new generation.
A Maou of pure logic.
And a cultivator from another cosmos, tearing through the word "incurable" like it was a suggestion.
On the bed, Ingvild's fingers twitched.
Barely.
But everyone saw it.
Then, with a tiny, fragile sound, she took a full, unlabored breath—not the shallow, mechanically-assisted rhythm she'd had for a century, but a deep inhale that moved her chest on its own.
The tension in the room snapped like an overdrawn bowstring.
Her eyelids fluttered.
Struggled.
Then opened.
Soft red eyes blinked up at the world for the first time since before the Great War.
The very first thing she saw was a man leaning over her, hand still resting lightly on her forehead, smile bright and warm and quietly triumphant.
"Welcome back," Ren said.
Ingvild stared at him.
Her lips parted.
"…Ren," she whispered, voice rough with disuse but clear.
He chuckled.
"Yeah," he said, his usual relaxed cadence flowing back in like a tide. "Told you I'd wake you up, didn't I?"
Tears spilled down her cheeks.
Her hands came up, clumsy and shaking, to touch his wrist—to confirm that he was real and not just another dream she'd lose when the tide pulled back.
He let her.
Behind him, Serafall made a strangled, half-sobbing sound.
"She—she actually—Ajuka, look!" she gasped.
Ajuka didn't answer at first.
He was staring at the monitors like a man trying to fit a dragon into a test tube.
Disease markers—gone.
Sleep Disease pattern—collapsed into inert feedback loops that no longer touched her vital structures.
Sacred Gear activity—stable, humming in a smooth, tidal rhythm instead of spiking wildly. Nereid Kyrie's sleep aura no longer wrapped around Ingvild's consciousness like a cage; it flowed outward, touching the edges of her Soul Palace like waves on a shore.
Magic circuits—harmonized, devil and human components no longer at war.
"This…" Ajuka breathed. "…This is a completely different… framework. No rejection. No decay. It's… cleaner than anything I've ever seen."
Sona's vision blurred.
She pressed a hand to her mouth, swallowing hard against the lump in her throat.
Ren glanced back at them, still smiling, eyes soft but steady.
"Told you," he said lightly. "Solved."