Demon Lord reborn as The Hero's Child

”I’ve heard everything.”

Kōya’s blood turned to ice.

He froze completely, his small boots rooted to the scarred earth of the training yard.

Kaela stood several paces away, the half-eaten apple still resting casually in her scarred hand. Her golden, feline eyes had narrowed into sharp, vertical slits, and the playful, boisterous expression she had worn only moments ago had completely evaporated, replaced by the terrifying, cold focus of an apex predator cornering its prey.

”You have nowhere to hide now.”

Her tufted ears twitched, locking onto the erratic, sudden spike in his heartbeat.

”And nowhere left to run.”

Kōya stared at her, a cold sweat breaking out across the back of his neck.

His ancient, tactical mind went completely, catastrophically blank.

*How much did she hear?*

He slowly, carefully shifted his gaze toward the porch of the house.

Professor Eldren was currently gathering his academic parchment and adjusting his robes. Seiya was already speaking with the mage in low, respectful tones about the academy arrangements, while Mizuki stood near the doorway, apparently entirely unaware of the lethal conversation unfolding in the yard.

Kōya swallowed hard, his throat dry as dust.

*Did she hear me aggressively cursing my demonic power?*

*Did she hear me analyzing the Hero’s holy mana?*

*Did she hear me speak the name Raizen Kurogane?*

Kaela took another slow, agonizingly loud bite of her stolen apple, the crunch echoing in the tense air.

”I have exceptional hearing, boy.”

Kōya’s dark eyes narrowed into defensive slits. ”How excellent?”

She smiled, a slow parting of lips that revealed the lethal curvature of her fangs.

”Excellent enough to hear someone whispering their darkest secrets to the trees from quite a considerable distance.”

Kōya’s stomach violently sank.

She pointed a long, calloused finger directly toward the deep shadows of the forest line.

”You talk to yourself a lot in the dark.”

Kōya’s face twitched, his jaw clenching so hard his teeth ached.

*Damn it.*

She had heard absolutely everything. Every frustrated, arrogant mutter. Every venomous question directed at the gods. Every single time he had violently cursed his own fragile human body for being weak, and every time he had demanded to know why his left hand categorically refused to channel the abyssal mana.

She knew.

But how much did she actually comprehend?

Kaela casually tossed the apple core over her shoulder into the tall grass.

”Don’t worry, little boy. I don’t know exactly *what* you are hiding inside that tiny chest of yours.”

Kōya’s eyes sharpened, a microscopic fraction of relief warring with his paranoia.

”But I know you are hiding *something*,” she purred, stepping closer, her boots making absolutely no sound against the dirt. ”And whatever it is, it is fundamentally, terrifyingly different from the parlor tricks you showed the good Professor Eldren.”

Kōya said absolutely nothing. He maintained a mask of stone, refusing to incriminate himself.

She stopped directly in front of him, looming over his small frame.

”If you don’t want me marching inside and telling your legendary father what you do in the woods...”

Her smile widened into something undeniably sadistic.

”...then you are going to show me absolutely everything.”

Kōya’s expression changed, his brow furrowing in deep confusion. ”What?”

”I want to fight you.”

”You just watched me fight Professor Eldren.”

”That wasn’t a fight,” she scoffed, rolling her shoulders. ”That was a sterile, controlled academic assessment. It was boring.”

Her scarred fingers closed lovingly around the leather hilt of one of her curved swords.

”This will be entirely different.”

Kōya stared up at her, sensing the genuine, unbridled bloodlust rolling off her skin in waves.

From the porch, Professor Eldren suddenly looked over, catching the shift in the atmosphere.

”An unofficial fight?” Eldren asked, raising a bushy eyebrow.

Kaela glanced toward him, her smile never wavering. ”Just a little sparring. To test his endurance.”

Professor Eldren sighed heavily, rubbing his temples. ”Please, try not to completely destroy the training grounds. The Amane family has been very hospitable.”

”No promises,” she chimed.

Kōya looked desperately toward Seiya.

His father was already walking toward the heavy wooden door with Professor Eldren.

”We’ve finished the official assessment,” Eldren said over his shoulder. ”Kōya has passed with flying colors.”

Kōya blinked, temporarily derailed from his panic.

*I passed?*

Seiya smiled warmly at his son from the porch. ”Congratulations, Kōya.”

”Wait,” Kōya said, his voice cracking slightly as he pointed a trembling finger toward the Beastwoman. ”She wants to fight me. Right now.”

Seiya stopped. He looked at the heavily armed, grinning Beastwoman.

Then he looked down at his tiny, stiff son.

Then back at her.

Seiya smiled, a bright, utterly unhelpful grin.

”Good luck.”

Kōya’s jaw literally dropped. ”Father!”

Seiya just laughed a booming, hearty sound as he walked inside. ”Professor, let’s finish the rest of this endless academy paperwork over tea.”

Professor Eldren nodded gracefully. ”Agreed.”

Mizuki followed the men toward the house. Before crossing the threshold, she paused and glanced back at Kōya, her eyes filled with a terrifying, knowing calm.

”Don’t hurt yourself, Kōya.”

Kōya stared in absolute betrayal at his parents as they disappeared inside the warm cottage.

*They’re seriously leaving me out here with this maniac?*

The heavy door clicked shut.

An oppressive, suffocating silence immediately settled over the ruined clearing.

Kaela drew both of her beautifully curved steel swords. The metallic *shing* rang sharply in the quiet air.

Kōya violently tightened his grip around his battered wooden practice sword, his knuckles turning stark white.

She rolled her shoulders, her neck popping loudly.

”Ready?”

Kōya sank low into his defensive stance, bringing the wooden blade up. ”As ready as I’ll ever be.”

”Good.”

She casually tossed one of her steel swords away. It landed point-down in the grass with a heavy thud, burying itself inches into the soil.

Kōya blinked, deeply offended. ”You’re only using one?”

She shrugged lazily. ”I don’t want you crying and complaining to your mother afterward that it was unfair.”

Kōya’s eyebrow twitched violently.

*She’s insulting me before the blood is even drawn.*

He stepped forward, the grass crunching under his boots.

Kaela smiled, her golden eyes flashing.

”Come.”

Kōya exploded forward.

His first strike was ruthless, aiming a sweeping, bone-breaking arc straight toward her leading leg.

She didn’t even bother to block it with her steel.

Her empty, scarred hand simply shot out, catching the flat side of his wooden sword in mid-swing, flawlessly redirecting the immense kinetic momentum entirely away from her body.

Kōya’s eyes widened in sheer disbelief.

*What?*

She stepped backward, flowing like water.

Kōya immediately followed, refusing to yield the offensive. He swung a vicious overhead arc.

She shifted her body by a fraction of an inch, the wood passing harmlessly by her ear.

Another strike, aiming for the ribs.

She redirected it with a flick of her wrist.

Another.

She moved completely around him with an almost insulting, ghostly ease.

Kōya gritted his teeth, frustration boiling in his chest.

*She’s reading my biomechanical movements before I even commit to the strike.*

He aggressively changed his angle. This time, he feinted high and aimed a devastating thrust incredibly low.

Her empty hand moved with blinding speed. The wooden blade slid harmlessly past her hip, guided by her palm.

Then, her heavy leather boot came up.

**BOOM!**

The front kick struck Kōya directly in the absolute center of his chest.

His small body launched backward as if fired from a cannon.

”Gah!”

He flew several meters through the air before slamming one foot violently into the ground. He stabbed his wooden sword into the earth to act as a brake. The blade screamed as it dragged across the soil, his boots carving two long, deep trenches through the dirt before he finally ground to a halt.

Kōya stayed low, breathing heavily, his lungs burning from the impact.

Kaela hadn’t moved from her spot. She rested her steel sword casually on her shoulder.

”Not bad.”

Kōya pulled his wooden sword free from the dirt, his eyes burning with fury. ”You call that not bad?”

”Yes.” She smiled, her fangs glinting. ”Because you’re miraculously still standing.”

Kōya roared and rushed forward.

His sword came in a blistering horizontal arc from the side.

She leaned fluidly away.

He immediately reversed the exact motion, leveraging his core, and brought the wooden blade violently upward toward her chin.

Kaela’s eyes widened slightly in genuine surprise.

She tilted her head backward at the last possible microsecond. The heavy wooden blade passed mere millimeters from her face, the wind of the strike ruffling her wild hair.

Kōya almost smiled.

*Got you.*

Then, her closed fist slammed brutally into his stomach.

**THUD!**

Kōya instantly folded in half, all the air violently expelled from his lungs.

Before his ancient mind could even process the recovery, another heavy punch struck his shoulder, deadening the nerve.

Then another to his ribs.

Then another to his jaw.

**THUD! THUD! THUD!**

His small body jerked backward like a broken puppet with every devastating impact.

Kaela moved with terrifying, surgical precision. She wasn’t trying to kill him; she was dismantling him.

Punch.

Elbow.

Sweep.

Kick.

Punch.

Kōya was being brutally battered entirely across the clearing, treated like a helpless, infantile training dummy.

”Stop moving!” Kōya gasped, swinging blindly.

”I’m trying!” she mocked, side-stepping effortlessly.

Another devastating punch to his guard.

**BOOM!**

Kōya hit the ground hard, the dirt exploding around him.

He rolled frantically to avoid being pinned.

Kaela appeared instantly above him, blotting out the sun.

He raised his wooden sword in a desperate guard.

Her fist stopped directly in front of his face, the sheer kinetic wind from the halted impact brushing violently across his bruised cheek.

She smiled, looking down at him.

”Your fundamental sword technique isn’t bad,” she assessed clinically.

Kōya slowly, painfully lowered the wooden sword, his chest heaving. ”But?”

”Your footwork is absolutely, fundamentally terrible.”

Kōya’s expression darkened into pure hatred.

*I know.*

He pushed himself up off the dirt, his arms trembling. His breathing had become ragged and wet. His body hurt absolutely everywhere, his muscles screaming in protest.

Yet, something incredibly deep, ancient, and unbroken inside his soul categorically refused to stay down.

Kaela tilted her head, her golden ears twitching.

”You’re still holding back.”

Kōya froze, wiping a trickle of blood from his lip. ”What makes you think that?”

”I can hear your heartbeat, boy.” Her eyes narrowed dangerously. She pointed the tip of her steel sword directly toward his right hand. ”That pathetic display isn’t all you can do.”

Kōya looked down at his small hand.

Then back at her.

The absolute faintest trace of ghostly, purple-blue demonic energy crawled slowly across his knuckles, vibrating with suppressed fury.

Kaela smiled, a look of profound satisfaction. ”There it is.”

Kōya exhaled a long, shaky breath.

*Fine.*

If she wanted to see the abyss...

He would show her exactly why the world had feared him.

Demonic mana exploded violently from his right arm.

**FWOOM!**

Blazing, freezing blue-violet flames wrapped entirely around the wooden sword, the sheer density of the aura causing the air pressure in the clearing to plummet.

Kaela’s ears twitched rapidly, her eyes widening in thrill. ”I knew it.”

Kōya completely disappeared from his position.

A massive, dark slash tore horizontally across the clearing.

**SHRAAAK!**

Kaela jumped violently backward. The demonic slash carved deeply through the earth where she had just been standing, leaving a smoking, blackened trench in the grass.

Kōya swung again, pivoting on his heel.

Another massive crescent of concentrated demonic energy ripped through the air, screaming like a dying animal.

She twisted sideways, contorting her spine. The apocalyptic attack passed mere inches beside her.

Another.

She ducked, the blue fire singeing the tips of her hair.

Another.

She slid across the scorched ground on her knees.

Another.

She backflipped, kicking off a tree trunk.

Kōya abandoned all restraint, relentlessly attacking.

**SHRAK!**

**SHRAK!**

**SHRAK!**

Dark, violently compressed crescents tore the Amane training ground into a smoking, pulverized wasteland.

Kaela moved through the apocalyptic barrage completely effortlessly.

Left.

Right.

Forward.

Back.

She slipped perfectly between the lethal gaps in each attack with a frightening, otherworldly precision, reading the trajectory of the demonic mana before it even left his blade.

Kōya’s breathing grew incredibly heavy, his small mana core burning in agony.

”You’re remarkably talented,” she called out, landing lightly on a completely un-scorched patch of grass. ”I won’t tell anyone about your dark little secret.”

Kōya’s eyes widened in relief, lowering his sword slightly. ”But...”

Her smile changed. The playful thrill vanished, replaced by an ancient, terrifying bloodlust.

”...this is getting boring.”

Kōya’s blood instantly ran ice cold.

”What?”

She tightened her scarred grip around her remaining steel sword.

A faint, boiling crimson glow appeared along the sharp edge of the blade.

Then, it violently erupted.

**FWOOM!**

Blinding, roaring red energy engulfed the weapon entirely. The air itself seemed to literally tremble and warp under the sheer, oppressive heat of the aura.

Glowing crimson markings of fiery, furious mana spread rapidly along the steel, pulsing like veins.

Kōya stared in absolute horror.

*That’s not ordinary human mana. That’s an unusual mana composition*

Kaela’s golden eyes became impossibly sharp, the pupils narrowing to hairline slits.

Her playful expression was entirely gone. She looked like a god of war.

”I said, I wanted to make this interesting.”

The oppressive crimson aura intensified, melting the frost his demonic mana had left on the grass.

Kōya involuntarily took one step backward.

For the very first time since this unofficial fight began...

The Supreme Demon Lord was genuinely, physically afraid.

*She’s actually serious. She might kill me.*

Kaela vanished.

Kōya barely managed to raise his flaming wooden sword in time.

**CLANG!**

Their weapons collided with the force of an exploding star.

A blinding flash of freezing violet and roaring crimson exploded between them, a shockwave that flattened the tall grass for fifty yards.

Kōya’s small arms shook violently under the pressure, the bones in his forearms groaning.

Her sheer physical strength was completely overwhelming.

He roared, pushing forward with all his demonic might.

She simply smiled and pushed harder.

The ground directly beneath Kōya’s boots cracked and caved in under the downward pressure.

”Not bad,” she whispered over the crossed blades.

She broke the lock and swung again.

Kōya barely blocked it, his knees buckling.

**CLANG!**

Again.

**CLANG!**

Again.

**CLANG!**

Every single collision sent violent, blinding flashes of opposing mana echoing across the clearing. Violet demonic energy fought desperately against the crimson fury of the beast.

Kōya, refusing to die twice, forced himself aggressively forward.

He violently twisted his body, using his smaller stature to his advantage. His wooden, aura-coated sword slipped perfectly beneath her steel guard.

He struck upward.

A razor-thin line appeared across her leather-clad forearm.

Bright red blood surfaced.

Kaela stopped her assault. She looked down at the bleeding cut on her arm.

Then, she smiled. A terrifying, genuine smile.

”You actually cut me.”

Kōya stood ten feet away, breathing heavily, leaning on his sword.

”I told you...” He raised his glowing blade, his dark eyes unyielding. ”...I’m not weak.”

Her smile widened, her fangs fully exposed.

”I never said you were.”

She attacked with the speed of a falling guillotine.

Kōya blocked, but the overwhelming concussive force drove him violently backward, his boots skidding through the dirt.

He desperately tried to counter.

She fluidly changed direction mid-swing, defying physics.

Their blades crossed again, sparks raining down on them.

Kōya felt his center of balance completely slipping.

*Too fast. She’s too fast.*

Her footwork was completely, fundamentally different from his. She wasn’t simply stronger; she commanded the physical space. She knew exactly where his feet would move before his brain even sent the signal to move them.

He tried frantically to retreat.

Too late.

Her crimson blade swept toward him in a devastating, unavoidable arc.

Kōya raised his wooden sword in a desperate, final guard.

**CLANG!**

The heavy strike smashed completely through his guard, knocking the wooden sword wide.

He stumbled wildly. His body twisted awkwardly as he tried desperately to recover his footing and avoid falling face-first into her steel.

His hand reached out blindly, purely on instinct, seeking anything to grab onto to anchor his balance.

He grabbed something.

Something soft. Something he absolutely, under penalty of death, should not have grabbed.

Silence.

The roaring crimson aura. The violent violet flames. The crack of weapons. It all instantly ceased.

The entire clearing became deathly, suffocatingly still.

Kōya froze in place.

The Beastwoman froze perfectly in place.

Her face slowly, inevitably turned a violent, burning shade of crimson red.

Her tufted ears flattened completely against her skull.

Her left eye twitched.

Kōya, suspended in mid-stumble with his hand firmly grasping her chest, slowly looked down at his own hand.

Then, he looked slowly back up at her face.

”I...”

She stared down at him, her golden eyes dilated with sheer, unadulterated murderous intent.

”You... little pervert.”

Kōya’s face went completely pale, all the blood draining to his boots.

”It was an accident!” he shrieked, instantly letting go and jumping back.

Her eyebrow twitched harder, a vein bulging in her forehead.

”I didn’t mean to!” Kōya stammered in absolute terror.

Panic overriding his ancient intellect, he immediately tried to physically demonstrate the biomechanical error.

”I was falling backward, and my hand just went like this—” He aggressively pantomimed the grasping motion in the air.

Her face became even redder, radiating literal heat.

”Don’t demonstrate it!” she roared.

Kōya instantly dropped his hands to his sides, standing at rigid attention.

”Right.”

The crimson aura around her steel sword suddenly, violently intensified, erupting into a roaring pillar of flame.

Kaede’s smile was completely gone. She looked like a demon straight out of the deepest abyss.

”You little...”

Kōya took a frantic step backward, his wooden sword forgotten.

”Wait.”

She slowly raised her steel sword high above her head.

”I can explain the physics ob f the fall.”

”You’re going to explain it while I break every single bone in your tiny body,” she hissed, stepping forward.

”I said it was an accident!”

”You’re making it significantly worse by talking!”

”I know!”

She charged, the ground exploding beneath her boots.

Kōya’s eyes widened to the size of dinner plates.

”WAIT!”

**BOOOOOOM!**

A massive, unnatural cloud exploded across the clearing, blocking out the sun.

Water came crashing down from above with the force of a tidal wave.

Rain. But not ordinary rain.

An entire, hyper-condensed monsoon storm had appeared directly over their heads in an instant.

The Beastwoman was drenched instantly, slammed into the mud by the sheer volume of water. Her roaring crimson aura vanished beneath the freezing torrent, extinguished with a loud, pathetic *hiss*.

Kōya stood perfectly frozen, shivering violently as freezing water cascaded over his head.

Kaela’s wild hair hung heavily over her face. Her ears drooped pathetically. Her muscular tail was soaked, dragging in the mud.

Kōya slowly, terrified, looked toward the porch of the house.

Mizuki stood outside in the dry shade. One hand was raised, glowing with an intense, absolute blue mana.

Her expression was terrifyingly, serenely calm.

”What...”

She looked directly at Kōya, her eyes promising a very long grounding.

”...did you do?”

Kōya instantly pointed an accusing, trembling finger at the dripping Beastwoman. ”Nothing!”

The Beastwoman pointed her steel sword directly at him, coughing up water. ”He’s a filthy little pervert!”

Mizuki’s eyes widened in sheer, motherly shock.

Kōya’s ancient soul nearly left his mortal body in sheer embarrassment.

”IT WAS A BIOMECHANICAL ACCIDENT!”

The heavy wooden door opened. Seiya and Professor Eldren stepped out onto the porch, appearing right behind Mizuki.

Seiya, holding a teacup, looked from his drenched, panicked son, to the drenched, furious kaede, and finally to the utterly destroyed, cratered, smoking ruin that used to be his training ground.

He blinked slowly.

Professor Eldren elegantly adjusted his dry robes, clearing his throat.

”I believe my academic work here is finished,” Eldren noted mildly.

Seiya nodded slowly, taking a sip of his tea. ”Yes. Safe travels, Professor.”

Mizuki lowered her glowing hand, stopping the monsoon. She looked at her shivering son.

”Kōya.”

Kōya stood at attention. ”Yes, Mother?”

”Inside. Now.”

Kōya lowered his head in utter defeat. ”Yes, Mother.”

He began the long, humiliating walk of shame toward the porch.

Behind him, kaela suddenly burst into loud, genuine laughter, wiping mud from her face.

”You really are funny, Little Pervert.”

Kōya’s head snapped toward her, his face burning hotter than her crimson aura.

”Don’t call me that!”

She smiled, her fangs glinting.

”Little Pervert.”

”I said stop!”

”Little. Pervert.”

Kōya covered his face with his small hands.

My new life is completely, irreparably ruined.

Kaela gracefully sheathed her steel sword, the metallic click echoing in the damp air.

Her fierce expression softened into something resembling respect.

”Don’t worry, kid.”

Kōya stopped and looked back at her through his fingers.

”I won’t tell anyone at the academy about your dark little secret,” she said quietly, her ears twitching.

His expression instantly became dead serious. ”You promise?”

”I promise.”

She looked around at the destroyed, smoking craters of the training ground, admiring the sheer devastation he had caused.

”But I want something heavily in return for my silence.”

”What?” Kōya asked warily.

She pointed a wet finger at the wooden sword lying discarded in the mud.

”You’re incredibly talented.”

Then, she pointed directly at his muddy boots.

”But your physical technique is violently incomplete.”

Kōya looked down, shame warring with pride. ”My footwork.”

”Exactly.”

She bent down and picked up her second steel sword from the wet grass, sliding it smoothly into its scabbard.

”You’ve learned exactly how to swing a heavy sword with power.”

She rested her hands on the hilts of both weapons at her hips.

”But you haven’t learned how to actually move with one.”

Kōya stared at her, the truth of her words ringing in his ears.

She crossed her arms over her chest.

”And if you want to survive the monsters in the world outside this quiet little village...”

Her golden eyes sharpened, flashing with the wisdom of a veteran who had survived hell.

”...you’ll need significantly more than just raw, unrefined power.”

Kōya looked slowly at the ruined clearing. At the deep cuts he had made with demonic fury, which she had effortlessly danced through. At his own battered, bruised, and soaking wet body.

Then, he looked back at the fierce woman standing before him.

He finally understood.

His raw demonic power was undeniably strong. His ancient combat instincts were sharp.

But neither of those things was enough in this new, fragile body. Not yet.

He had spent weeks foolishly believing that simply awakening his old power would make him invincible again. Today, in the mud and the rain, she had shown him the brutal truth.

Raw power was only one piece of a true weapon. The vessel had to be forged to handle it.

Kaela lowered her arms, waiting.

”So?”

Kōya slowly raised his heavy head, his dark eyes filled with a new, humbling resolve.

”Will you teach me?”

She smiled, a wide, predatory grin.

”With absolute pleasure.”

Then, her grin turned slightly sadistic as she added, ”But I’m warning you right now.”

Kōya sighed, his shoulders slumping. ”What?”

She pointed a finger right between his eyes.

”I’m going to beat that terrible footwork out of you.”

Kōya stared at her.

Somehow, he suspected she meant it literally.

For some inexplicable reason, he deeply felt that the grueling Royal Academy assessment had actually been the easy part of his day.

And somewhere inside the warm house, his parents were probably still sitting at the kitchen table, wondering exactly what in the name of the gods their young son had done to aggressively earn the permanent title of ’Little Pervert’.