The Duke’s Daughter’s Mission to Seduce the Demon King～Humanity’s final gambit: a political marriage with the Demon KIng! …Hang on, but what am I supposed to do if the Demon King is a girl!?～ 1

Part One

Chapter 1: A Political Marriage to Save Humanity
Humanity was on the brink of extinction.

Demons had appeared without warning, destroying over half the nations on the continent and slaughtering countless people.

The Demon King and her four subordinates.
A mere five demons had driven humanity to the edge.

No matter what the remnants of humanity tried, they could not defeat the five demons, including the Demon King. If the war continued, humanity would be annihilated—and that was no metaphor.

But they couldn’t simply give up.

They were no match in terms of power. Acknowledging that, they had to play every card they had.

One of those cards was this:
A political marriage between the Demon King and Cecilia Lynted, a duke’s daughter, and the establishment of a ‘temporary’ ceasefire. And so, Cecilia had come to the demons’ stronghold.

She had crimson eyes, beautiful golden hair that flowed to her waist, and a slender yet perfectly toned physique. Noble and beautiful, Cecilia was the perfect pawn for a political marriage.

She belonged to the largest of the few remaining nations and hailed from the prestigious Duke Lynted’s family. With her distinguished lineage, refined education, and impeccable manners—not to mention her beauty—her duty was singular.

She was to seduce the Demon King and persuade her to ensure humanity’s definitive safety.

Of course, it was crucial that humanity’s true intentions remained hidden, which was why a bride of noble blood was the first choice for this political marriage. Otherwise, it would have been better to use someone who specialized only in making men fall.

And so, among the handmaidens accompanying Cecilia were personnel of just that sort. They were the backup, the second plan, in case her attempt to seduce the Demon King failed.

Whether it was Cecilia or one of the women disguised as her handmaidens, if just one of them could make the Demon King fall for her so completely that she would listen to anything she said, they would secure a lasting peace, not just a ‘temporary’ one.

Therefore.
Therefore.
Therefore.

The being seated on the throne was a woman.
The absolute pinnacle of the five demons—the Demon King. That was the title given to the woman sitting on the throne.

I wasn’t told about this.
I was never told that the ultimate power known as the Demon King was a woman!

Countless black tentacles erupted from the absolute being’s back, forming a dress-like shape, while scales covering her arms glistened like black gloves. These monstrous features intertwined in a strange harmony, creating a feminine silhouette. In fact, her chest was far more assertive than Cecilia’s.

And besides, her face was undeniably that of a woman.
Even to Cecilia, who had been polished to the peak of beauty by the combined efforts of surviving humanity and was clad in a pure white dress, she was beautiful.

The dark-haired, dark-eyed Demon King stared at Cecilia with inorganic eyes that betrayed no emotion. Meanwhile, the four other demons standing before the throne layered their words with scorn.

“Tch! Why does someone like her get to marry the Demon King-sama?”

“This, too, must be the will of the Goddess.”

“Keeheehee☆ Nephy, you have such wicked taste.”

“I hope this provides a little amusement.”

A girl in a maid outfit with wings of armament made of swords and spears; a woman in a jet-black nun’s habit with white hair and odd eyes, one blue and one red; a woman in tattered leather armor and a black cloak, with fiery red hair falling untamed to her waist; and a woman who appeared to be the strategist, dressed like a dancer with tanned skin, sharp, twisted red horns, and eyes that swirled with black and white.

The four demons. Each one was powerful enough to destroy a nation single-handedly, but Cecilia had no time to dwell on such trivialities.

Her mind was racing, focused entirely on one point.

Everyone had assumed that a being called the Demon King would be male.

In truth, any human who got close enough to see the Demon King’s form had been killed without exception. And any attempt to scout the demon stronghold was met with an immediate counterattack, so perhaps it couldn’t be helped. Still, if the leader of the demons was a woman, shouldn’t she be called a Demon Queen or something similar?!

Even so.

Her mind threatened to shut down from the shock, but Cecilia somehow managed to rally her faltering spirit.

Her mission hadn’t changed.
Whether the Demon King was a woman or not, if she couldn’t be seduced, humanity’s extinction awaited. If she gave up now, everything she held dear would be swallowed by blood and death.

Then I must press forward.
I will overcome any absurdity and seduce this ultimate threat.

“I still can’t accept this. What’s this about a political marriage?! Why must our great and beloved Demon King-sama take a human woman as her bride?!”

A woman blocked her path, as if to crush that first step.

Wings of armament made of swords and spears, and a maid outfit. Based on eyewitness reports, this had to be Lapience.

From her recorded statements during the war, it was clear she was the most devoted to the Demon King among the demons. At any moment, she looked ready to bring the crude iron rod clutched in her hand, a weapon far taller than herself, crashing down. That was how easily the creatures called demons dealt death.

A single glance from her overflowed with unfathomable killing intent.
It was so dense that even Cecilia, who was a stranger to life-or-death battles, could feel it vividly.

A chill ran down Cecilia’s spine.
Faced with certain death, she felt an urge to flee.

And yet, she continued.
This was the demon stronghold. She had known from the start that just returning alive, let alone succeeding in her mission, would be a monumental task.

Still, she had sworn to fight with all her might if there was even the slightest chance. That was why Cecilia Lynted, the duke’s daughter, was standing here now.

Therefore.
Therefore!

“I am here for a political marriage.”

“Huh? That’s what I’m—!”

“And this political marriage was agreed upon through discussions between both humanity and the demons. Do you alone have the authority to overturn that decision?”

If I show weakness here, it’s over.
What charm is there in a timid, cowardly opponent?

No, perhaps a weak, pitiable approach that inspires a desire to protect might work. But Cecilia Lynted had never lived her life that way. If she tried to change her strategy now, her facade would surely crumble.

So, the correct move here was to stand firm.
She must not yield her will, her worth, her strength.

If she failed with this approach, it would simply mean that ‘strong-willed women’ were not to the Demon King’s taste. In that case, the women she had brought with her as handmaidens would try a different approach.

So, by staking her life on her own way of being, she could probe the Demon King’s preferences. Even if she failed, it would connect to the ‘next’ attempt. As long as someone eventually seduced the Demon King, it would be humanity’s victory.

“Enough of your prattling! You’re just a human!”

In that instant, Lapience swung her massive weapon. A direct hit would have splattered Cecilia—who only knew enough magic for a noble’s self-defense—into bloody pieces.

SPLAT!!!
Instead, it was Lapience who exploded. Her silhouette completely disintegrated, showering Cecilia’s pure white dress in a spray of blood and gore.

“…!?”

It was a blow delivered by magic.
Cecilia’s eyes could discern the ‘color’ of it, but that changed nothing.

As a scream almost escaped Cecilia’s lips, the voice of ‘her’—the one who had unleashed the magic and killed Lapience—pierced the air.

“Stop that.”

The voice was inorganic.
The speaker was a woman whose face, like a Noh mask, revealed no emotion.

The Demon King.
The monster who reigned at the pinnacle of the demons had uttered just that one phrase.

“Um…”

“What is it?”

“Did… did you, Demon King-sama… just kill this demon?”

“Yes.”

“But… why?”

“Lapience was the one who tried to attack first. Being mean is wrong.”

It was so casual.
Far too casual for a matter of life and death.

Lapience attacked first. So I killed her. The Demon King’s expressionless face spoke volumes, implying there was nothing more to it.

This was the Demon King.
A single word from her would have been enough to make Lapience back down, yet murder was the first option that came to her mind. This was the incomprehensible monster she had to seduce if humanity was to have a future.

“More importantly,”

Lapience had just proven that a single choice could lead to death.

In this hopelessly desperate situation, Cecilia refused to break, keeping her eyes fixed forward.

A political marriage.
All to seduce the Demon King under that pretense.

“What’s a political marriage?”

…………
…………
…………

“What… do you mean, ‘what’?”

“I mean, what is it?”

It was said so matter-of-factly.
The political marriage that held the fate of humanity. The lifeline that she and the others had clung to, an agreement forged through talks between demons and humans.

And the Demon King herself didn’t even know about it?

“Nephy. What’s a political marriage?”

“Hmm? The humans came to us with some laughable proposal about a political marriage. It sounded like it might kill some time, so I accepted it on my own.”

The strategist called Nephy—the woman with the dancer-like clothes, tanned skin, and red horns protruding from her forehead—said it without a hint of remorse.

Cecilia’s cheek twitched. This was bad.

The entire premise, the political marriage itself, was decided on a whim by the strategist. This meant the Demon King could very well dismiss the entire engagement with a simple “I can’t be bothered.”

The political marriage had been established.
But the will of the one at the top had not been involved. In the first place, there was almost no benefit for the overwhelmingly superior demon side to accept a proposal like a political marriage from humanity. It wouldn’t be strange at all if it fell apart.

Still, she had to press on.
No matter how absurd it was, she had to overcome it, or humanity would perish.

That’s what she thought this was about.
But the Demon King was on a completely different level.

“That’s not what I mean. What does ‘political marriage’ mean?”

“Hah? Don’t tell me you don’t even know what a marriage is, Nephy?”

“I don’t.”

Cecilia no longer knew what the right answer was.

How could she have possibly anticipated that the Demon King wouldn’t even understand the meaning of the words “political marriage”?

“Well, the concept of marriage is foreign to us demons. Let’s see… a political marriage is where you connect two beings of important standing to solidify a cooperative relationship and gain mutual benefits. It’s a human custom, so it’s not like we have any obligation to follow it.”

“…?”

“Basically, it means ‘let’s be friends from now on, though with plenty of ulterior motives.’ Observing the foolish humans who pin their hopes on something like a political marriage, thinking they can control our actions, should be a good way to kill time, don’t you think? Ahaha!”

“Keeheehee☆ Only you would have such a wicked sense of humor,” said the woman with fiery red hair and eyes.

Just then, the Demon King spoke.

“Cecilia.”

“Y-Yes.”

“So, does this mean you’ll be keeping me company to kill time?”

For a moment, just a single moment, Cecilia almost screamed, ignoring the entire premise of her mission. But she was Cecilia Lynted, and she swallowed it down before it could surface.

Killing time.
This monster had trampled over half the continent and spread untold death—and after all that, she had the audacity to say she was bored. It was impossible not to feel a surge of anger.

And yet.
Cecilia connected the thought again and again.

I will save humanity. To do that, she would even grovel before the Demon King who had killed so many. She would seduce her and neutralize her so that no one else would die.

If she could make such a fairytale a reality, she would do anything.

That was why Cecilia Lynted was standing here now.

“Of course. After all, we are to be married. I will ensure that you never think of your marriage to me as mere ‘boredom’.”

She would, without fail, no matter what, save humanity with this honey trap—

“Oh, I left Lapience dead.”

Just then, the Demon King said it so casually, as if it were nothing. The scattered pieces of flesh gathered together and solidified into the shape of a woman.

“…Huh…?”

Lapience.
The demon woman who had undoubtedly died just moments ago was resurrected right before Cecilia’s eyes.

It wasn’t a magical illusion, nor had she been barely alive and regenerated. A life form that had been definitively dead was brought back to life in an instant.

—Skill: Mystic Eyes. A type of skill that only a select few are born with. Unlike magic, skills cannot be acquired through effort.

The skill Cecilia had been born with allowed her to see the flow of magical energy released outside the body. That was all.

And it was limited to external magical energy.

Magical energy, the source of most magic and skills, cannot be perceived by the five senses. While it’s said that magical energy differs from person to person, the only way to observe these differences is to use the Mystic Eyes to discern its ‘color.’ But that was the extent of its ability.

Since it couldn’t read the magical energy within a body, it couldn’t be used for applications like predicting the timing of a spell to counter it. It was only after magic or a skill was output that it could be observed, so the advantage wasn’t that significant. It could make invisible magic or skills visible, but by then, a direct hit would be all but certain. Considering that the ‘power’ that revived the dead was too fast for her to even perceive the flow of magic before it was over, its usefulness was clearly limited.

And yet, even a ‘power’ like this was considered rare among humans. Compared to that, one could understand just how powerful the Demon King, who could even revive the dead, truly was.

“Lapience.”

“Y-Yes?!”

“It’s good to be energetic, but causing pain is not. If you’re too mean, I’ll kill you and won’t bring you back for a week.”

“I-I’m so sorry!”

“Good. As long as you understand.”

The Demon King nodded at the slightly teary-eyed Lapience, her own expression unchanging.

The skill of regeneration.
While rare, there were humans who could use it. But of course, resurrecting the dead was impossible for humans.

This was information that had never been observed during the war. It was only natural, as the demons had never been pushed back far enough for any of them to be killed.

This was an extraordinary power befitting the Demon King.
How many other unconfirmed powers was she hiding?

In any case, if this was truly an unprecedented skill that could overturn even death, a skill never before observed…

If she could seduce the Demon King, could she not only prevent further deaths but also bring back all the humans killed by the demons?

Could such a convenient, perfect happy ending truly be possible?

(This is a more welcome development than I could have ever wished for.)

Quietly, firmly.
Cecilia Lynted hardened her resolve once more.

(For the sake of humanity, I will seduce the Demon King, no matter what!)

…Of course, it would only be a short while later, after she had calmed down, that she would be clutching her head, wondering how on earth a woman was supposed to seduce another woman.