January 1st, 2025.
A day meant to welcome the New Year.A day when people around the world were laughing, celebrating, counting down together.
And also—the day humanity would never forget.
On that day, in a world inhabited by eight billion people, something appeared.Something that everyone, sooner or later, would come to call by the same name.
The Door.
No one knew where they came from.No one knew what they truly were.
On January 1st, 2025, a total of ten thousand Doors appeared across the world—across every country, every continent, without exception.
Each Door took the form of a wooden gate, standing 2.1 meters tall and one meter wide. From the outside, they looked ordinary. Plain. Harmless. Just a simple wooden door standing in the middle of streets, fields, buildings, or empty land.
Nothing about their appearance suggested danger.
But in truth, opening a Door meant being dragged into another world.
A world that could be an ancient ruin swallowed by time, an endless forest, a burning desert, an ocean without shore or bottom, or places no human mind could fully describe.
All such locations beyond the Door were collectively called "Places."
Inside these Places existed not only mystery, fear, and overwhelming grandeur—but also monsters.
Creatures of countless shapes and sizes.
Beasts that would attack without warning, tear flesh apart, crush bones, and devour anything alive the moment they sensed weakness.
Not everyone could open a Door and enter a Place.
When a Door appeared, it would randomly select a single person within a radius of fifty kilometers. That person would be marked as "The Chosen."
Once chosen, a black key-shaped mark would appear on the back of their hand—a mark that served as a license.A requirement.
Only those marked as The Chosen could open a Door.Anyone without the mark would find the Door completely unresponsive.
The Doors could not be destroyed.They could not be moved.
Nations across the world attempted everything. Heavy machinery. Advanced weapons. Even nuclear warheads.
Nothing worked.
Not even a scratch.
The only way to make a Door disappear was to enter it—and destroy the Core of the Place beyond.
Cores were spherical objects whose locations could not be predicted. They might lie at the farthest end of the Place, be hidden inside the body of a colossal monster, or exist somewhere no one would ever think to search.
And monsters were not the only danger.
Within many Places existed entire civilizations—races different from humanity, and sometimes even humans themselves. The inhabitants of these Places were almost always hostile toward the Chosen.
To them, the Chosen were enemies that had to be killed first.
Because once a Core was destroyed, the Place itself would vanish.
Their world.
Their home.
Gone.
For this reason, Chosen entering a Door often wore gloves, hiding the black mark on their hands.
When a Chosen successfully destroyed a Core, they would gain power.
What kind of power depended on what talents they displayed during their journey, how they fought, how they survived, and what kind of person they truly were. The Core would judge all of it and grant an ability accordingly.
So far, humanity had only confirmed ten types of Core:
-Core of Armor
- Core of Weapon
- Core of Symbol
- Core of Energy
- Core of Element
- Core of Form
- Core of Summon
- Core of Cultivation
- Core of Technology
- Core of Manipulation
Whether more Cores existed remained unknown.
Among the Chosen, strength was not equal.
Their level depended on how many Doors they had passed and the color of those Doors:
- White Door
- Yellow Door
- Orange Door
- Red Door
- Grey Door
- Black Door
Each successful destruction of a Core granted a Chosen a "Step Beyond," allowing them to ascend to a higher rank:
- The Opener
- The Descender
- The Ascendant
- The Integrated
- The Architect
- The Paramount
Monsters were ranked as well.
Their hierarchy mirrored humanity's—but their power did not.
From weakest to most terrifying:
-The Spawn
-The Blooming
-The Predator
-The Aberration
-The Apex Horror
-The Calamity
At the same rank, monsters were almost always stronger than humans. They were born inside Places, forced to evolve simply to survive. Combat was their nature.
There was another problem.
What if a Chosen failed to destroy the Core?
Simple.
Unless the Place contained an established civilization, the Door would release every monster inside. And once unleashed, those creatures would massacre every living being they encountered—without mercy.
And what if a Chosen chose not to open the Door at all?
After twenty-four hours, the Door would open on its own.
There was no escape.
The only solution was for the Chosen to enter the Door, reach the Place, and destroy the Core.
Simple to say.Almost impossible to do.
On January 1st, 2025, all ten thousand Doors were challenged.
All of them failed.
Ten thousand Chosen.Not a single survivor.Not one Core destroyed.
And so, every Door released its monsters.
That day marked a true apocalypse.
Creatures from ten thousand Places poured into the world, spreading slaughter without restraint. Nations fought back and evacuated civilians, but the modern weapons humanity once took pride in looked like toys before the monsters.
Fortunately—or unfortunately—the released creatures were only Spawn-level. They could block bullets, but bombs and missiles could still kill them.
Even so, it took three months to exterminate them all.
By the end of it, humanity's population had dropped from eight billion to five billion.Three billion people were dead.
Elderly.
Children.
No one was spared.
Countries were left in ruins. Facing extinction, the surviving nations united under a single banner.
They called it the Human Alliance.
From that point on, fifty to one hundred Doors appeared every year.
No one succeeded.
Until ten years later.
December 2nd, 2035.
The first human destroyed a Core.
The first Opener was born.
His name was Hallibert Greymond.
He became a symbol. A legend. He founded the Greymond family, a lineage that still existed to this day.
Following his example, more Chosen began to succeed. Humanity entered the Era of the Chosen.
Even so, the success rate remained cruelly low. Out of one hundred Doors, only ten Chosen survived.
As Door levels increased, the numbers dropped even further.
Those who achieved Step Beyond became rarer still.
Worse yet, the appearance of Doors caused the Earth itself to expand—tripling in size. Failed Doors released stronger and stronger monsters, forcing humanity to retreat.
Half of Earth was lost.
This half became a paradise—for monsters.
That situation had continued for five hundred years.
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Recalling everything he knew about the Doors, Ash stared out the car window, rain streaking across the glass.
He wondered—
'What will come for me next?'