Backflow
One day, colossal sinkholes—the Abyss—appeared across the Earth, and the world changed.
It was around that same time that the Awakened, those who could wield Cores, first emerged.
Beings gifted with special powers that ordinary people could never possess. Among them, the few who bore exceptionally strong or uniquely suited Cores would enter the Abyss to purify it, hunting down the monsters within.
And so, to raise outstanding Awakened of their own, the nations of the world established special educational facilities reserved solely for them.
One of these was the National Gaon Special Academy—the undisputed finest institution in South Korea for cultivating Awakened minors.
A handful of other Awakened-exclusive schools existed as well, but among them all, Gaon was special.
First, there was the sheer size of its campus. With an entire artificial island near Incheon devoted to the school, Gaon had earned the nickname "Academy City."
And second—it was the only Awakened school in the world that possessed an active Abyss on its grounds.
Gaon's students could enter the Abyss on a regular basis through practical training classes held on campus. In other words, they accumulated far more real experience than graduates of any other school.
That was why, even among Awakened, a Gaon graduate commanded greater advantages—higher salaries, for instance.
"Unnie, when I graduate, I'll get you out of here. I promise!"
That was what Jihyo had said on the day Jiwoo's admission to Gaon was decided.
Jiwoo, who had spent practically her whole life confined indoors, heard the words and simply shook her head.
"I'm fine. I'm perfectly happy with things the way they are."
Of course, there were moments when the walls felt suffocating. It might have been easier if she had never known the "outside" at all—but until the age of five, Jiwoo had lived what anyone would call an ordinary life.
Back then, the four of them—her parents, Jihyo, and Jiwoo—had lived together in a house of considerable size. She still remembered being led by the hand between laboratories and hospitals day after day. It must have been to repair her unstable Core.
Fortunately—or perhaps unfortunately—Jiwoo's family was wealthy, and as the owners of a pharmaceutical company, they had deep connections among the most influential figures in medicine and research.
Jiwoo's parents spared no expense or effort to save the daughter who had been born different from everyone else. Illegal experiments, inhumane methods—they were willing to try anything.
The long and short of it is that, thanks to them, the treatments proceeded smoothly enough.
Then, one day—
"Is it true? That you manufactured illegal drugs to save one child?"
The Chairman of Seolhwa Pharmaceuticals—Jiwoo's grandfather—summoned her parents. And then he gave his order.
"Kill it."
"Father, how could you say such a thing—!"
The Vice President of Seolhwa Pharmaceuticals and his wife had a social face to maintain. What would happen if word got out that they had resorted to criminal acts to save a single daughter? The damage might not end with Seolhwa's image merely taking a hit.
Still—was that truly the only reason the old man had ordered Jiwoo's death? She could never know for certain.
"A nail that sticks out. You pull it before someone trips over it."
Her parents opposed him fiercely, of course. But the Chairman was unyielding.
In the end, rather than kill Jiwoo, they procured a sprawling mansion and made her live there alone.
Everything had to be handled within those walls. Her treatments, her studies, her play—all of it.
No birth registration, no formal education even when the time came for it.
A being who existed, yet did not exist.
That was the life Jiwoo was made to live.
"Jiwoo, you understand, don't you? The outside is dangerous, so you must stay in the house. From now on, the doctor will come to us."
Even so, it was bearable. Her parents still cherished her.
But……
Even those parents passed away the year Jiwoo turned six. She was told it was a car accident.
Jiwoo never saw her parents' bodies. She wasn't even allowed to attend the funeral. That, too, was by her grandfather's order.
After her parents' deaths, no one came to see her anymore—except for Yoon Soyoung, the private tutor her parents had hired for her while they lived, and her one and only younger twin sister, Jihyo.
"After I graduate from Gaon, I'm going to inherit Grandfather's company. Then I'll develop the medicine to fix your Core, and……"
"Enough. Don't worry about me—just focus on doing well at school."
"There you go again. What's the point of me being happy all by myself? We're twins, remember?"
At Jihyo's words, Jiwoo had simply smiled.
Really, though.
Her sweet younger sister, who came to visit without fail every single vacation despite being under the old man's watchful eye. That kind, gentle child who always brought back piles of photos and videos for the sister who couldn't set foot outside.
If you're happy, then even if I spend my whole life in here and never leave, that's more than enough for me.
…That was what she had believed.
Turns out they were right—no one knows what life will bring.
At this very moment, Jiwoo was standing inside the National Gaon Special Academy.
With a name tag reading "Seol Jihyo" pinned over her left breast.
Seeing it in person, she realized it was a world apart from the photos and videos. The overwhelming grandeur truly lived up to its reputation as an Academy City.
And yet……
Why is nobody here?
She had been told in advance that a guide would come out to meet her, but no matter how long she waited, not so much as an ant appeared.
She had already spent thirty whole minutes staring blankly at the sky.
It was 8:50 in the morning. Classes would be starting any minute.
In the end, Jiwoo decided to make her own way to the High School Division Building.
It was fine. She didn't have much luggage, and she had a map. She could find it on her own, no problem.
…Or so she thought.
Is this not the right way?
Trusting a map when she had never once in her life walked anywhere by reading one—that had been her mistake.
While she was locked in a staring contest with the map, Jiwoo found she had wandered into some kind of empty lot. She lowered the map and looked around.
Come to think of it, the air around here did seem strangely dark.
…What is that?
A sudden gust of wind pulled her gaze toward it. The air was bitter and cold—hard to believe it was late spring. She could see trees torn up at random and asphalt split down the middle.
…Had there been an earthquake nearby?
As if drawn by something, she walked toward it. The cracked asphalt heaved faintly, like the skin of a living creature, and damp vapor seeped up through the fissures.
Her steps stopped in front of the yellow caution tape strung around the area like a spider's web.
This is……
Beyond the tape, a massive gaping hole yawned open. From its unfathomable depths, a strange keening sound drifted upward.
She knew at a glance what it was.
—The Abyss.
It's way bigger than it looked in the photos…?
She was standing at a distance, entertaining that idle thought, when—
WEEEEEOOOO—
An ominous siren split the air.
Jiwoo stumbled back a step and scanned her surroundings. A evacuation drill? What was that noise, all of a sudden? Before she could make sense of the situation, a vicious wind came howling in.
"Ah……!"
WHISH!
Her long hair whipped across her vision, and the map she'd been holding scattered into the gale like scraps of tissue paper. Trees shrieked and bent under the typhoon-strength gusts.
CRASH!
At last, a few of the trees gave up entirely, tearing out by the roots as they toppled.
Something was very wrong.
Instinctively, her eyes swept the area—and at the edge of her vision, Jiwoo spotted a grotesque shape.
A long, lurching shadow, moving with sluggish, unhinged grace. By its form and its size, it looked human. But……
"Grrk, grrrk—"
Its ragged, irregular breathing was laced with a wet, scraping sound, like claws raking a throat.
An Infected.
Ordinary Infected did not simply burst out of the Abyss—not unless something like this happened. Not unless the Abyss backflowed.
A backflow was no common occurrence. Trained Awakened regularly "purified" the interior and perimeter of the Abyss, keeping the pressure contained.
And this was a school packed to the brim with Awakened, no less. Even so, a backflow here was anything but normal.
Then it occurred to her—the news she'd watched that very morning with Soyoung.
Come to think of it, hadn't they said the Abyss beneath the Blue House had backflowed too……
"Krrk, grrrk!"
Sensing the warmth of a living creature, the thing began to bend and twist its body toward Jiwoo in a hideous, unnatural contortion. Black fluid dribbled from its mouth, frothing into a sticky foam—a single drop fell, plip, to the ground—
"KEEEEEEK!"
It launched itself like a coiled spring and came hurtling straight at her.
"……"
Jiwoo did not dodge.
A split second before its claws touched the nape of her neck, she gave her fingers the lightest flick—
WHOOSH!
One of the fallen trees nearby rose abruptly into the air, and then shot clean across the open ground.
CRUUUUNCH!
"Gkkh……!"
The tree slammed into the Infected dead-on.
It was over in an instant. Its neck snapped, the creature never reached Jiwoo—it simply dropped, thud, onto the pavement.
Dark, tar-black blood oozed out of the fallen Infected in slow rivulets.
Jiwoo stared at it with eyes devoid of any feeling, then bent down and retrieved her map from where it lay nearby.
Good. It didn't blow too far.
She blew the dust off the map with a soft puff, tucked it under her arm, and walked away without a backward glance.
She had to reach the High School Division Building before she was any later.
—About five minutes later.
"Wh-what the hell is this?!"
By the time school staff came scrambling to the scene, Jiwoo was already long gone.
All they found was the crushed corpse of an Infected, flattened like a boiled potato—and a single street tree, torn out roots and all.