Midnight.
A mountain pass led toward the town where the Kingdom's forces were stationed. Along that road, deep within a valley barely touched by moonlight, a single military unit advanced. At first glance, each member appeared almost human—but the horns growing from their heads were unmistakable proof that they were not.
They were demons.
Creatures whose outward appearance closely resembled humans, yet whose true nature differed fundamentally from humanity on a biological level. Without question, they were a kind of monster.
Despite possessing humanoid forms, intelligence, and emotions similar to humans, their mentality was no different from that of beasts. Like all monsters, they possessed an instinctive desire to prey upon humans.
Because they so closely resembled humans in appearance, they were truly humanity's natural enemy.
At present, they moved through the darkness night after night, on their way to attack the Kingdom's army—where a unit of the Demon King's forces was stationed.
Compared to humans, they far surpassed them in magical power and physical ability. The concept of defeat did not exist in their minds.
With magic incomprehensible to humans and physical prowess beyond human limits, they would trample their enemies.
Victory itself no longer occupied their thoughts—only the pleasure that would follow. Flaunting their magic, forcing others to submit, tasting human flesh—this was, to them, no different from a leisurely outing for humans.
And because of that—
They failed to notice.
They failed to realize that the poison gnawing at them had already spread everywhere.
At the rear of the unit walked a demon who resembled a human girl.
The girl, with pale pink hair hanging loosely, raised her face for a brief moment. A faint light flickered within her pupil-less eyes.
"So… it's time."
She whispered in a gentle yet utterly monotone voice. At the same time, she came to a halt, and black magical energy gathered in her hand.
That black magic quickly took the shape of a jewel-encrusted sword—one the girl herself had seen before.
"…?"
Sensing the magic, nearby demons began turning toward her all at once. But before they could react—
The poisonous girl moved.
She vaguely understood that she might already be in the process of breaking down.
At the very least, no other demon would do something like this.
Even knowing that, however, she was not the type who could restrain herself.
The noise erupted.
The sound of trampling feet.
The sound of slaughter.
The sound of magic.
Amidst it all, the girl swiftly cut down her kin who stood in her way.
Most of those who fell victim to the jewel-encrusted sword never comprehended what was happening. Certain of victory, drunk on arrogance, and thinking only of what would come afterward—no one could grasp this sudden aberration.
But that alone was not the sole reason for the massacre.
Several demons eventually recognized the abnormality, surrounded the girl, and attacked her with swords or prepared to cast spells.
They outnumbered her. Even cutting them down one by one with a sword would normally take time.
But the girl did not hesitate.
"Coiling process, decomposition phase."
The jewel-encrusted sword reverted back into black magic.
"Imitation Sword, Transformation Shift."
The black magic took the shape of a weapon once more—this time, a trident longer than the girl herself. When the demons saw the weapon change from a sword to a spear in an instant, their eyes widened in shock.
In that moment, the spear spun and struck in all directions.
Their bodies were torn apart, scattering like mist as magic poured from their wounds.
Only the demons hovering in the air remained, preparing to unleash magic from above.
"Imitation Sword, Transformation Shift."
Even as she held the spear, the girl transformed it into multiple daggers. She flung them from between her fingers.
The demons could not evade the ultra-high-speed projectiles. The blades pierced their hearts, throats, and skulls, and they fell.
Once again, only demons who had yet to comprehend the situation remained in her path.
The girl used one of the fallen demons as a foothold, leapt upward, reformed a retrieved dagger into a jewel-encrusted sword, and descended upon them.
In the darkness stood an executioner of betrayal, her face unseen, wielding a weapon that transformed for the sake of slaughter.
"…!"
Unable to understand what was happening—or even identify their attacker—the demons attempted a counterattack. But the girl was always two or three steps ahead.
She knew every member of this Demon King Army unit.
With her distinctive eyes—capable of seeing magical power, the same eyes that enabled her to use the spell Aerial Magic Mimicry—she had been observing them constantly for a long time.
With enough time and concentration to drive an ordinary person insane, she never stopped watching, waiting for her chance.
Their habits.
Their weaknesses.
The magic they used, the time it took to activate, and even the unique flow of magic just before activation—
She understood it all.
And so, without pause, she predicted their actions through the flow of their magic and always struck first.
She created weapons suited to the situation in an instant, then remade them again and again. Every movement was inspired by and refined from the human and demon warriors she had fought in the past.
As a result, her style had form—but no fixed shape. It was in constant flux.
No warrior could keep up with those changes.
She spun her body again and again to conceal her movements, wielding ever-changing weapons without pause. The methods of killing she had honed through endless practice and a relentless pursuit of versatility and efficiency looked, to an observer, closer to a dance than to combat.
The darkness was absolute. Even demons with sharp night vision could not clearly see their enemy in such a sudden situation. Yet even if the girl could not discern their forms, she could see with perfect clarity the flow of magic coursing through their bodies. And for that reason, despite their numerical advantage, this battlefield belonged entirely to her.
To strike first against each of them, she had memorized the flow of magic behind every one of their actions—indeed, she had paved the way for this massacre itself.
The way she had carried it out over time was exactly like a poison spreading gradually through the body.
After eliminating the demons in her path, the girl finally leapt toward the demon leading the unit.
"You… are you Leni?!"
That demon, far larger than the others, was without a doubt a general-class demon. Even if the girl unleashed all of her magical power, she would not normally be able to reach him.
Yet the demon girl, Leni, showed no trace of fear in her eyes. She turned the jewel-encrusted sword in her hand back into black magic, then generated new black magic in her other hand. The two masses transformed into a pair of hand axes, which she hurled at the general.
The spinning weapons flew toward him—but failed to strike.
A massive axe appeared in his grasp, blocking them.
"Great Whirlstrike Battle Axe, Bilwind."
That was the name of the general's weapon.
The faster it spun, the more the magical power embedded within its blade swelled, granting it more than twice the offensive force of an ordinary rotating axe. It was a magical axe possessed by no one but this general.
Without exception, weapons forged by demons for killing were masterpieces made of exotic materials—especially those of general rank.
"AAAAARGH!!"
Though shaken by Leni's sudden betrayal, the general immediately focused on destroying the enemy before him. He raised the axe above his head, spun it, and slammed it violently into the ground.
In that instant, the earth screamed.
The ground split apart, and debris rained down like a storm.
"—!?"
For the first time, Leni's expression shifted. Her eyes widened slightly as she adopted a defensive posture midair in response to the sudden impact.
The general did not miss that opening.
A massive arm—large enough to swallow most of Leni's slender body—emerged from behind the dust and seized her torso. She struggled, but could not break free.
I won't ask you why. But—
The grip tightened.
"You've really done it this time!! Because of you, everything has been destroyed!!"
He cursed her viciously, branding her a traitor.
A normal demon would have lost the will to fight from that alone.
But the executioner of betrayal slowly raised her face.
With cold, lifeless eyes devoid of light, she stared only at the demon general.
"You…?!"
Enraged, he attempted to crush her—but before he could,
Leni's lips moved slowly.
"Exphantasma— the spell that converts magical power into an explosion."
In that moment, an explosion erupted behind the general. The scattered debris turned into deadly shrapnel that tore into his back.
Protected by the general's massive armor, Leni avoided fatal damage. And the instant his grip loosened, she re-formed the jewel-encrusted sword in her right hand and stabbed it into his arm.
"Guh!?"
Unable to endure the pain, the general released her.
The explosion had been caused by one of the hand axes Leni had created earlier. After being deflected by the Great Whirlstrike Battle Axe, Bilwind, it had remained lodged in the canyon wall. When the general's strike shattered the ground, the axe fell along with the rubble and was buried behind him.
Leni had detonated the magic that formed that hand axe.
The explosion itself caused no severe damage—but it created a momentary opening.
And that was enough for Leni.
"Coiling process, decomposition phase."
She reverted the jewel-encrusted sword in both hands back into black magic.
"Do you dare to mock me again and again?"
The general turned in fury as he sensed the magic.
But without replying, Leni poured even more magic into the black mass returned from the sword.
—Evaluate the principle of creation,
—Envision the foundational framework,
—Copy the materials used in its construction,
—Imitate the techniques employed in its forging,
—Interact with the experiences that led to its growth,
—Reproduce the years of accumulation,
Surpass every process—
"Imitation Sword, Transformation Shift."
—Bind the illusion here, and make it a weapon.
"W-What is that…?"
The general was about to swing Bilwind once more, as if refusing to forgive her—but he froze, eyes and mouth wide open at the sight before him.
In Leni's hands was the very same weapon he wielded.
Another Great Whirlstrike Battle Axe, Bilwind.
Once again, the weapons forged by demons were masterpieces made of exotic materials. And these weapons were the result of the demons' own magic, refined through relentless training.
Demons took immense pride in their magic. They devoted their entire lives to mastering those unique spells.
In other words, for the demon who forged such a weapon, that weapon itself was the embodiment of their life's work in magic.
For it to be so easily copied—
No words could express his feelings.
"You bastard!!!"
With a twisted expression he had likely never worn in his life, the general roared.
His mind shattered. His thoughts no longer connected.
Was his pride trampled? No—this went far beyond that.
At that very moment, the general felt as though his entire life had been ground beneath someone's heel.
He could no longer stand.
He could no longer hold the axe.
He could no longer wield his techniques.
If there were words to describe his state, they would be: frozen by rage.
Using the arm that had been gripping her body as a foothold, Leni leapt upward. As if utterly indifferent to his fury, she spoke calmly.
"Mimicry Magic: Ervasen."
Leni's manufactured weapons lacked the precision to fully replicate the skill or power of their original wielders as he himself could. No matter how much she refined the weapon's quality—perhaps due to her nature as a demon—she fundamentally lacked the capacity for deep empathy.
Unlike him, who held at least a minimal level of respect for his weapon, such feelings meant nothing to her.
Thus, she could not use the same possession-like experience he relied upon.
But Leni did not need it.
She had acquired the general's techniques through Mimicry Magic—but the warrior she now envisioned was someone else entirely.
At that time, she had once attended a heroes' banquet. Among them was a warrior of exceptional skill.
If she could imitate the movements of a warrior who wielded the same type of weapon and possessed greater technique, there was no need to deliberately copy the original wielder's style.
—Memorize the sequence of magic,
—Refine the stored flow,
—Trace this path,
—Here and now, convert it into form.
Leni leapt into the air, spun her entire body in a spiraling motion, and swung the replicated Great Whirlstrike Battle Axe, Bilwind. She calculated four full rotations.
The axe blade, heated by charged magical power, descended from above the general's head.
That strike—combining the demon general's magical axe, the product of a lifetime of effort, with the technique of the greatest warrior in human history—
—Split the general's enraged roar, and his body along with it, cleanly in two.
The canyon road was reduced to ruins after the fierce battle, rubble scattered everywhere.
After her victory, Leni sat atop the debris, swinging her legs idly as she bit into an apple she had taken from her pocket.
She took another bite, clenching and opening her empty left hand as she reflected on the battle that had just ended.
"…That was dangerous this time."
As expected of a general-class opponent. Had even one of the three factors been missing—the ambush shock, the explosion of the discarded weapon, or the second shock of copying his weapon—Leni would have been crushed instantly.
She had never intended to fight head-on. That was why she had laid such meticulous groundwork and calculated everything before claiming victory.
The fact that it had escalated into an open battle was proof of a miscalculation.
Ideally, she wanted to finish things one-sidedly, far more efficiently.
"But… that last part was good."
Gathering black magic in her free hand, Leni gazed at the replicated Great Whirlstrike Battle Axe, Bilwind, and remembered—
The day she killed the demon who had once forced her into submission, at the summit of that mountain range.
On her way down, she happened upon a battle between another demon unit and a four-person adventuring party known as the "Hero Party."
There, Leni's eyes were stolen by the technique of a single dwarf warrior.
Eisen—the name of the warrior she considered the strongest.
She knew full well that her physical strength was still far from sufficient to perfectly replicate his style. Yet merely tracing his movements with her body had fundamentally altered the way she fought.
Eisen possessed overwhelming power, yet due to his dwarven stature, he was short.
From him, Leni learned how to maneuver against opponents far superior in physical size. Though she had copied and absorbed the movements of many warriors, Eisen's were the first to truly penetrate the foundation of her own style.
Leni had never felt respect for the original wielders of the weapons she copied, nor for the users of the techniques she imitated—but toward Eisen's techniques alone, she felt a uniquely close affinity.
"But still… it's pointless. In the end."
She raised her gaze to the sky, lost in thought.
The very fact that the situation had turned into a battle was itself a problem. At times, she had deliberately provoked combat to extract an opponent's techniques, and she had done so actively in the past.
But this opponent was different. They had been together for months, waiting for the success of this ambush. Even without fighting him directly, she had been observing him constantly. She had long since copied his movements in full.
For Leni, engaging in a fight when there was nothing left to gain was the height of inefficiency.
Because she lived by infiltrating Demon King Army units and stabbing them in the back at the right moment, Leni was forced to live in complete isolation.
She could never gain allies among humans—and demons, by definition, were prey she was meant to harvest.
That was why Leni needed to expand what she could do alone, pushing every ability she possessed to its absolute limit.
Among the warriors she copied, she carefully refined everything she felt was necessary to suit her own body. And to constantly observe demons—whether comrades or prey—she relentlessly trained her eyes to read the flow of magic.
Her ability to detect magic had increased dramatically, and she even used it as leverage to infiltrate Demon King Army units.
She also developed techniques to suppress her own magic and conceal her true capabilities.
She had improved greatly—not only in surface-level stats.
Insight. Observation. Focus. Situational judgment—and the ability to turn the battlefield itself into an ideal hunting ground, as she had done this time.
Leni had pushed every ability she deemed necessary for her hunt to its utmost limit.
Naturally, that included the precision of weapon creation she obtained through mimicking "him."
And yet, she began to feel the limits of hunting alone.
She felt herself growing stronger—but that alone was no longer enough.
If only there were a way to better utilize factors that did not rely solely on herself.
"…Ah."
She murmured softly, tapping the apple with her finger.
Due to the nature of her hunting style, Leni would infiltrate Demon King Army units for a period of time before attacking them from behind. While belonging to those units, she sometimes fought human soldiers—Kingdom troops, Imperial soldiers, and the like.
In that process, she had personally killed many humans.
But Leni viewed those battlefields only as opportunities to focus on training while infiltrating. She copied the movements of any warrior she encountered and made them her own. After all, she was still a demon, and she spared no effort in honing her own magic—Mimicry Magic: Ervasen.
But now that she thought about it—
At those times, the other demons were completely focused on the human warriors and mages.
Wasn't that an ideal situation, with perfect opportunities everywhere to strike from behind?
Why hadn't she realized it sooner?
"I can make use of humans."
Leni knew how to gain the trust of demons.
She had even manipulated demons with words before, guiding them to hunting grounds by exploiting the value they placed on her ability to detect magic.
This time, she could do the same with humans—and crash them into demons.
The problem lay in how.
After acquiring a degree of human common sense and behavior in that village, Leni could hide among humans for long periods, so long as she did nothing. But because the races were fundamentally different, infiltrating human ranks was nothing like infiltrating demons, and earning their trust was impossible.
What she wanted was a way to manipulate humans in a short time and turn them into demon-hunting units.
And the answer she reached was—
"Information."
She whispered it.
After being forced to fight almost exclusively solo for so long, she had come to understand its importance all too painfully.
Humans, weaker in strength, valued it far more than demons. And because Leni constantly fought from a disadvantaged position, she understood that better than anyone.
"I'll simply leak it—to humans. Information about demons."
Where their current unit was stationed. Which city they planned to attack.
She would pass that information to nearby human soldiers and deliberately make them clash.
"Or maybe the reverse would be better."
Provide information to both sides and make them collide.
By adjusting the timing of the leaks, she could even manipulate the place and time of the clash—if everything went well.
That would make it exceedingly easy to prepare the optimal conditions for hunting.
She trusted her magic detection ability and her capacity to infiltrate human settlements. Those were the very traits that made demons consider her "useful for exterminating humans."
Whether she received orders at the right time or offered suggestions herself, it would be easy to create a pretext to slip into human society.
"It's decided. From now on, I'll provide information to the human side as well—and hunt more efficiently."
Concluding that this would be more effective, she bit into her apple once again.
After chewing for a while, she stopped swinging her legs and looked up at the night sky once more.
Her expression—eyes slightly narrowed—was strangely serious.
"…But if I do that, there will be one nuisance."
She had discovered a more efficient hunting method, but in exchange, she realized she had created an annoying problem.
In the worst case, humans might witness her hunting grounds.
Until now, every demon she had lured into her hunting grounds had fallen victim to her imitation weapons, so there had been no actual witnesses.
But if she used this method, humans might learn of her hunts—and that knowledge could eventually reach the demons she truly intended to hunt.
That meant any human who witnessed her hunting would have to be killed by Leni herself.
She would take on the task of cleaning up humans—a role previously handled by other demons. Depending on timing, the risk would be enormous.
Viewed positively, it could be seen as an opportunity to fully refine her magic against human warriors after achieving her goal of eliminating demons—but being alone, she might allow some to escape.
In other words, she would have no time to comfortably focus on training.
Even so… it could not be avoided.
Through countless battles, Leni had learned that prioritizing efficiency always required some form of sacrifice.
The number of humans she would have to kill with her own hands would increase—but still—
—In the end, the total number of victims would be fewer.
"…?"
For a brief moment, Leni felt a faint sense of discomfort at the vagueness clouding her thoughts, but she quickly dismissed it.
Having settled on her future course, she leapt down from the rubble and walked a short distance along the canyon road.
Ahead, she could see the lights of a town—the very town the demon unit she had just slaughtered was meant to attack.
"…"
She stared at it for a while, then turned her back and walked away.
Perhaps it was because of the lingering sweetness of the apple…
Her lips were slightly relaxed.
Whether Leni herself noticed it or not, no one could say.
And yet—
The emptiness in her heart was never filled.