It's been more than ten years since the "Demon King" was defeated by a "hero" summoned from another world.
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The "hero" had already returned to his world, and the number of demons created by the "demon King" was rapidly decreasing.
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In the past, the world was overflowing with monsters, but now they were hiding in the depths of forests and caves.
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――The world was run by humans and demi-humans.
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A world without demons.
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A world of peace.
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A world where people fight with each other.
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A world where humans and demi-humans help each other.
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A world where there was no "Demon King".
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A world where there were no "heroes".
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A world governed by three rulers who had traveled together with the hero.
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That was this world.
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"A world saved by a hero from another world" ――Eusware.
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A world said to have been created by the goddess Eusware.
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A world where there were swords and magic, and where spirits, demi-humans, demons, and humans
lived.
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A world where demons would perish in the not-too-distant future.
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――It was supposed to.
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That was what everyone thought.
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Humans, spirits, demi-humans, demons, goddesses―― even the "hero" thought so.
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Because isn't it was it supposed to be?
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There was no "demon king" who could create demons.
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Then, there was no way for the demons to increase anymore...
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                                                                                   ...

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One of the three rulers, the Magic Queen "Leticia".
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Fonteau, a northern country ruled by Leticia.
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Leticia, the mage who traveled together with the hero and defeated the Demon King.
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She was a genius and a natural disaster who defeated the Demon King at the age of 18.
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Her magic was tremendous, and although she was not as strong as the Demon King or the hero, she was probably the strongest, even compared with the elves who were skilled at magic.
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She thought so, and those around her.
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She was now more than thirty years old, but her beauty had been further refined, and her luster had even increased as she had given birth to a child.
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She could have been called a beautiful girl at the time, but now she had grown into what they would call a beautiful woman.
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Long, beautiful, silky soft silver hair. She had large red eyes and an almost inhuman appearance. The sharpness of her eyes was also one of her charms.
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And her ears were slightly pointed, perhaps due to the mixture of elven blood.
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Not as pronounced as an elf's, but not as round as a human ear either.
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It was the part that Leticia hated, and the part that the hero loved.
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A human and an elf. An elf and a human.
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That was Leticia.
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Leticia Fonteau. She was the Queen of Magic and a mage who defeated the demon king. She had two children with the hero.
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However, her body did not deteriorate in the slightest. Rather, she had the glamour of a mother.
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Leticia liked to wear white clothes, which was unusual for an elf.
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Elves were said to be the people of the forest, and many of them prefer to dress in bright green color, but Letitia wore a white dress. The dress was decorated luxuriously with many layers of fine embroidery, but the fabric was thin and does not hide the queen's voluptuous body.
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Her shoulders were bare, her rich breasts peeking out the top. However, the pure white dress covered her from her chest to her ankles.
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With slender arms, ample breasts, the waist that might break if someone hugged it tightly was swaying gently in a tight dress.
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There was a sense of charm to it even if it was hidden.
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Many men have lewd thoughts at the sight of her.
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Even the "hero" was like that.
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The hero whom she traveled with when she was still in her youth also lusted after his traveling companions many times, the mage Leticia and the hunter Frey.
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Since that time, she had noticed her beauty. And unconsciously used it as a weapon.
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Now, she used it intentionally.
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Men's eyes were naturally drawn to her ample breasts, which shook slightly as she walked down the hallway.
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Despite being protected by her clothes and undergarments, one could feel the richness and softness of her body just from looking.
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It tempted male soldiers. It was an invigorating feast for their eyes.
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Her beauty, her body, and the cold atmosphere kept other nobles away.
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All of them were beautiful.
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Simply a beautiful queen.
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That was Leticia.
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"Good morning, Mother."
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The one who greeted her was Meltia, the older daughter wearing a sky blue dress.
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She had her mother's silver hair and an adorable young face.
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She was a woman of full-grown age, but her height was a head shorter than most women her age.
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And yet, those breasts. The symbolic part of a woman was abundantly fruitful.
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But that doesn't mean that it was due to obesity.
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From the lovely face to the shoulders that could be called slender, the abundantly fruitful chest, and the thin waist that was not even a little painful to squeeze with a corset.
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The buttocks were also rich and fruitful for her age.
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That was Meltia.
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"Good morning, Mel. Are you going to school today?"
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"Yes, mother. When I finish breakfast, then I'll be going to school."
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"I see. Work hard."
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"Yes."
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That was all for their conversation.
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The mother and daughter pass each other as they talk a little. Meltia bowed slightly and gave way.
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Royalty was such a troublesome thing.
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She recalled that when she was traveling with the hero, she was having fun.
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She could talk to him as friends, without any title of nobility or royalty.
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It was such a fun, dazzling, and beautiful memory.
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She could not help but think that one day it might be good for her daughter to experience something similar.
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She knew it was very difficult.
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She walked while thinking about such things, but eventually, she reached a door
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She knocked lightly, but there was no answer.
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She tried to open the door, but it was locked and the doorknob wouldn't turn.
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She probably knew that, and without surprise, her glossy lips faintly spun an incantation.
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Unlocking magic.
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Even family members need privacy, but not minding it, she unlocked it and entered the room.
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A bed with a canopy and luxurious furniture that was typical of royalty.
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Leticia's family preferred a simple room, but being royalty, they need to look good.
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Even if it was in a private room where the other nobles wouldn't see.
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There was still a bulge on the canopied bed despite the sun already being up in the sky.
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Leticia let out a sigh and moved closer to the bulge.
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"Maria"
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In truth, this kind of thing should be done by the chamberlain, not the queen, but Leticia was not going to yield on this one. There was some resistance to the idea of showing her daughter's trifling appearance to others, but she also wanted to cherish her relationship with her family despite her busy life as the queen.
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She called her name several times while gently shaking the bulge on the bed.
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After repeating it for a while, a black hair came out from the bulge.
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The complete opposite of Leticia and Meltia.
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The darkness of night. Deep black - the same color as the hero, his hair.
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Her beloved daughter "Mariabelle" had strongly inherited the blood of the hero.
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She had glossy black hair, and her eyes were also black.
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However, her skin was the same fine color as Leticia's.
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Although frugal and thrifty sounds good, she does not dress up properly, which was a problem for the royal family.
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She thought that she was very similar to her father, the hero.
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He, too, was not interested in acquiring anything other than what he needed. He was not interested in anything luxurious, just the essentials for traveling.
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Although nobles didn’t view it that favorably.
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She thought that Mariabelle was a lot like the hero. Leticia loved that about Mariabelle. The queen and her daughter, it was troublesome for the royal family, but.

When she looked at this girl, she could remember the hero who was no longer with them. Leticia lovingly stroked the black hair that peeked out from the bed as she thought about nostalgic past.

It was a very important thing.
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"Wake up. You'll be late for school."
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"......Is it that time already?"
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"Jeez... Like your father, you're not a morning person."
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"Muu..."
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With that small smile, Mariabelle's cheeks puffed up slightly.
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She guessed she doesn't like to be compared to her father.

She's going to be 18 this year, and she's still as childish as ever, she thought to herself as she smiled.

But there was nothing she could do about it. Her black hair, similar to the man Leticia loved, inevitably reminded her of the hero.

However, it doesn't mean that she's not seeing her as her daughter. She loved her daughter just as much as she loved the hero.

Thinking that, She stroked her soft hair as though she were combing it.
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"Fufu, you have beautiful hair."
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"But everyone in the school thinks it's disgusting."
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"I see."
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Black hair was rare in this world.

Or rather, there were probably no black-haired people in this country except for Mariabelle, who was of the hero bloodline.

That's why they were rare, feared, and looked at oddly.

She was very sad about that.

The color of the hero was a heresy in this world.
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"But I'm sure someone will love your hair someday."
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"I hope so......."
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She muttered, as though she had given up somewhat.

Her voice made Leticia's heart tighten.

Even though she loved her so much, this girl was trying to hate the world.

There was no magic in this world that could change the color of her hair or eyes.

Leticia stroked her glossy black colored hair so that she would know that she loved her daughter and her hair.

Mariabelle also surrendered herself to her mother's love.

She hand combed her hair after waking up from sleep. This was the only time she loved.

Such a peaceful time.

The demon king was defeated by the hero, and it was a peaceful morning that seemed to last forever.
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Such a happy moment.
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                                                                                   ...



The magic kingdom of Fonteau.

In the northernmost part of the kingdom, there was a cave where the magical silver mithril was mined about ten years ago.

Now, the magical silver had been mined out and the cave had become a dead cave, a place where no one would come.

It was a place of dampness and stagnation, where no sunlight reached the depths and where the grudges from the people who died from the collapse of the mining process accumulate.

However, it was not silent, with occasional drops of water dripping from the cave ceiling and the voices of the bats that roosted there echoing.

Bats squeaked, water droplets scraped the rocks, and several insects that would make a woman or child scream if they saw them ran behind the rocks.
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It was such a horrible, dirty, distorted, gloomy, and stagnant place.

In a sense, it was also peaceful.

Bats flew, insects crawled on the ground, and vengeful spirits proclaimed their despair.

It had been going on since the end of the mining of mithril, and it was going to continue.

But it would end.

Today, at this time, this "peace" would end.

And then...

A bat let out a strange low voice and fell to the ground.

Around the neck of the fallen bat was a single insect the size of a thumb.

It had a paralyzing stinger in its mouth that was used to paralyze its prey and eat them.
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It spent days climbing up the rocky wall, slowly ascending, moving forward so that the bat would not notice, and killed it with the paralyzing poison.

It finally caught its prey.
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The insects have no emotions, but they certainly squealed with delight.

It was a natural thing in the natural world. It had been and would continue, the reason for life.

――But who could have predicted that this logic would produce the worst possible result?

To prey on the fallen bat, the insect spits out a thin tentacle from its mouth.

The tentacles emit an acid that dissolved it little by little before it was eaten.

The insect's diet was not very large.

It dissolved the skin on the neck of the bat and ate a small amount of flesh from it.

That was the end of the meal.

The remainder would be eaten by insects that could not climb the rock wall or drop the bats from the ceiling.
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There would soon be nothing left.

They would even eat the bones.

The insects tried to gather around the bat's carcass, and a slight dragging sound echoed through the cave.

Startled by the sound and vibration, the insects scattered.

The darkness of the cave. What emerged from it was a distortion. It was a newborn monster.

There was a thud, a sound that had never been heard in the cave before.

Upon closer inspection, It was a "dark slime" that seemed to distort the cave's darkness.

More than ten years ago, it wasn't a rare monster, the Black Ooze.

It was a mid-level slime monster, and if it lived long enough, a monster of a certain strength.
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But that was only if it lived long enough.

A newborn slime was no better than a dog or other domestic animal. It was only the size of an infant's fist.

In truth, it was probably doomed to rot away without catching any prey or to be swarmed by insects and eaten alive.

But this slime had prey in front of it.

And it was bigger than the slime.

Following its instincts, the slime took the bat carcass into its body. The slime, which had previously been the size of an infant's fist, instantly grew after taking the bat into its body.

The slime gradually digested the prey it had taken into its body and turned it into nourishment.

It was lucky.
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And worst of all―― it could be bad luck.

If this was just a slime of the lowest rank.

No, if it had been any other slime.

Its fate would have been the same as it had rotted away without catching any prey.

But the Black Ooze got its food.

And then a change occurred.

The slime, which had been the size of an infant's fist, took in a bat and instantly grew larger.

It was a characteristic of the Black Ooze.

It instantly converted the digested nutrition and increased its mass.

Now that it had the nourishment of a bat, no small insect could kill this slime anymore.

――The only things that could kill this slime in the cave now would be the bats that was clinging to the ceiling, the lizards that lived deep inside the cave, and the wild dogs near the entrance.

But this slime was also smart. Or perhaps it was intelligent.

It didn't bother with larger prey, but instead sought out and preyed on small insects from behind the rocks.

It was the worst.

The insects in the cave could rival the number of stars in the sky.

It devoured them all.
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Following its instincts, it greedily ate and ate and ate.

And it grew in volume.

After a few days, it ascended the wall and caught a bat.

The bat thrashed its wings, but once the slime caught it, it could not escape.

The lizard sank its fangs into it, but by then it had grown to a size that a lizard was now helpless against it.

It wasn't able to digest the insect's carapace, which had a paralyzing poison. And being so small, it gave little nutrition.

However, it gave the slime an interesting "ability".

Paralyzing poison was now added to the slime's liquid.

This would make predation even easier.

After devouring the bats, lizards, and insects at the back of the cave, the slime extended its tentacles to the wild dogs near the entrance.
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It must have realized that its liquid had paralyzing properties.

It intentionally fed a tentacle to a wild dog and preyed on it after going into convulsions.

Once it had devoured all the wild dogs near the entrance, the slime returned to the cave.

It doesn't understand anything like homing instinct, but for the slime, this was its home.

The only thing in this cave now was this slime and the grudge that resided in this cave.

That was all.

The once quiet and peaceful cave was now a cave of death, where only grudges of vengeful spirits dwell.

By that time, the slime had grown to the size of a cow.

More than ten years ago, when the hero and the demon king fought.

The slime was as big as an ordinary cow.

But now that no demons were being born, Black Oozes were only seen in picture books.
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Everyone believed in peace and thought that it would last forever.

The time of the Demon King was now gone, and they wouldn't give up their happiness.

And that was why.

Right now, no one realized that "a monster was born".

Then, about a month passed.

When it had eaten all the wild dogs in the area, the inhabitants of the village near the cave finally began to wonder.

The village used to be a prosperous miner's town, but it became deserted when the magical silver stopped being extracted.

Only a dozen or so people were living in this rural village, and they make their living by dairy farming.

The village was full of old people, and they used to have to deal with wild dogs that attacked their livestock, but recently there have been no such attacks.
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They wondered.

Even though there was food in the mountains, they were not the kind of animals that would be satisfied with just that.

Having learned the taste of livestock, they relentlessly attacked them.

They use traps and killed them many times, but they still could not protect all of their livestock.

There were too many wild dogs.

And yet, there were none these days.

Have they given up? Someone thought so, but they quickly denied it.

Wild beasts don't have such straightforward thoughts.

But the wild dogs have indeed stopped attacking livestock.

It was strange, but they thought it was another miracle of the goddess Eusware, and decided to pray.
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It was a country village.

But even in such a rural village, there were always old men with a lot of blood in their veins.

He grabbed his weapon, put on his gear, and headed for the mountains.

He wanted to find out what had happened to the wild dogs.

The other villagers stopped him, but the old man did not listen to them.

The old man was convinced that he was strong.

He had killed many monsters in his younger days, not to mention slimes and goblins, and he and his friends had even killed mid-level demons such as ogres.
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He was convinced that even in his old age, his strength had not diminished in the slightest.

After a few hours of ascending the mountain, He began to feel out of breath, so he sat down on a rock to rest.

Climbing a mountain was too much for an old body.

He drank water as though he was bathing in it and exhaled.

He had already climbed a long way up the mountain. There was only a magic silver mine ahead of here.

But still, there were no wild dogs in sight.

He didn't even see any wild rabbits or other animals.

What was going on?

His intuition told him that something was going on.

His intuition was still sharp, even in his old age.

But his body was getting old.

――The next thing he knew, his old body had stopped moving.

Paralysis.

The paralyzing poison was poured into his body that he did not notice.

The effect was immediate.

The paralyzing poison from the slime, which was now the size of a cow, was as powerful as its mass.

In short, it was too powerful for the old man.

The poison easily stopped not only the movement of his body but even his heart.

The old man died, unable to understand what had happened to him.

The slime then preyed on the old man.

Slowly, slowly, slowly.

......And then the worst-case scenario rose.

On this day, the black slime acquired "knowledge".

Knowledge of monster killing, knowledge of humans, knowledge of life ...and sex.

No one, not even the slime, was aware of it.
 
This slime was a mutant.

It took away the characteristics of its prey.

The paralyzing poison of an insect.

Human knowledge.

What if the first person it ate was a woman?

If the first person it ate had been a woman, it would have taken the "pregnancy" property, which would have been worse.

But the first person it ate was a human man, albeit an old one.

The slime got it.

Knowledge of humans, knowledge of life, knowledge of how to impregnate a woman.

Humans were sinful beings.

After all, they were the only race that could impregnate not only their kind, but also different races such as elves, sirens, and beastmen.

The world still doesn't know.

The world still doesn't know that "a monster was born"...