Nanase Haruka, a stunning beauty with waist-length emerald green hair, was a student in the high school division of the Babel Academy within the Hero Academy, and she held the positions of student council vice president and disciplinary committee chairwoman.
A girl of true justice.
The fact that she could serve as vice president in a hero academy spoke volumes about her extraordinary abilities—not just her strength as a hero, but also her beauty and intelligence, making her an elite in every sense.
In Babel Academy, the one she admired the most was naturally the student council president—Hikami Kyouya.
He was the most outstanding student in the history of the academy, on the verge of advancing to S-rank Hero, a student so perfect that there was hardly any flaw to be found.
Of course, her admiration wasn't out of romantic affection, but purely the reverence toward an exceptional strong individual.
And so, when the president suddenly vanished out of nowhere, a figure appeared the very next second where he had disappeared.
This person had long golden-red hair with grey-white tips falling over his shoulders. On top of his head were a pair of twisted, uneven horns.
He wasn't human—this Haruka could say with certainty.
He was humanity's enemy—this too, she was certain of.
Even more terrifyingly, this being had just effortlessly slain Suruga Andou, one of the six leaders of the White Knight Order(a group on par with the managing force of Babel Academy, the COCOON)—an SS-rank hero (Savior), all with a mere wave of the hand.
There was no doubt: this man was the master of darkness, the ruler of shadow, the enemy of the world, the nemesis of the gods and of all heroes—he was the one known as the Demon King.
He reached out as if to grasp the air, and from the void, pulled out a mysterious cube inscribed with strange runes. At the same time, he seemed to be talking to someone unseen.
"Do you know what happens if you lose this thing?"
"Are you familiar with Calabi–Yau space? What do you think happens when matter gets mixed up in a space like that?"
It seemed like he was muttering to himself, speaking in confusing and ominous riddles.
Calabi–Yau space?
As vice president, Haruka was well-versed in knowledge and had a basic understanding of what that meant.
From the perspective of modern science, Calabi–Yau (or "Cal-Yau") space refers to a compactified high-dimensional space.
So, what exactly is the structure of a "Cal-Yau" space?
It's a very bizarre, hard-to-describe space. You could think of it like this: imagine a flat sheet of paper with no creases at all, and then crumple it into a ball—well, that's roughly what this space looks like. But in reality, the twists and turns of this space are far more complex than that simple crumpling.
It's like a dragon curling in on itself, looping back around, forming knots upon knots—completely devoid of pattern or regularity.
If a person were to exist within such a "Cal-Yau" space, they might experience something incredible—it'd be like being inside a house full of mirrors, walls surrounding you at every turn.
Everywhere you look, you'd see reflections of yourself, and depending on the direction you gaze, you might even see your own back.
When you reach out to touch it, surprisingly, you might actually feel your own back.
Fascinating, right?
But don't think you only reached out a straight arm's length to do that.
In reality, your arm might have twisted and looped around countless times within that chaotic, lawless space.
You might even see your own hand distorted, unnaturally elongated like rubber, or passing straight through your body without feeling a thing.
Now… what if a person was blended with a "Cal-Yau" space?
The next second, something suddenly materialized in the air where President Kyoya had vanished. Haruka was stunned—then immediately—
"Urghhh—!!"
She vomited.
That thing was far too grotesque and terrifying. She couldn't believe something so bizarre could exist in the world. Maybe it was just like those monsters from Lovecraftian myth.
How to describe it… It looked like a tumor. A grotesquely colorful, pulsating mass of flesh. No—calling it a tumor would be too kind.
What in the world was this thing?
Suddenly, Haruka spotted an eyeball—an eyeball embedded with teeth and fingers around it. Her blood ran cold. She began to recognize familiar human features.
"P-P-President Kyoya…?"
Her voice rasped with a scream of disbelief.
That grotesque mass was alive—and seemed to be the Kyoya, who had vanished only moments earlier. It seemed to be producing some kind of eerie, incomprehensible sound.
Perhaps a scream of rejection and agony—before seemingly falling into unconsciousness.
Right now, Kyoya was like a perfectly flat sheet of paper that had been crumpled into an indescribably horrifying lump—an abomination that would drive anyone insane upon seeing it.
His internal organs had been twisted, pulled inside out, and randomly mixed with other parts of his body.
By all accounts, he should be dead, right?
No.
Because of the abnormal nature of the extradimensional space, Kyoya had not suffered any physical damage at all. That's right—not a single injury.
Despite appearing like a corpse made of mismatched body parts, he was still whole and alive.
And that was the most terrifying part.
Unable to locate his mouth, unable to receive nourishment—would he starve to death?
Where was his mouth?
No one knew.
Haruka couldn't handle it—neither physically nor mentally. Every second she looked at that thing, her entire body screamed with revulsion.
Sweat poured down her face, her body trembled uncontrollably, and she nearly vomited her internal organs.
Disgust.
Horror.
Revulsion.
This thing shouldn't exist—it was the kind of image that would leave a lifelong trauma with a single glance. Even Hell probably wouldn't have anything more unbearable than this.
The sounds of people collapsing snapped her out of her trance. Haruka realized some of her companions had fainted, their minds overwhelmed by the horror.
It was only then—when one of those collapsed comrades dropped out of her view—that she finally noticed a figure standing in her field of vision, one that her subconscious had refused to acknowledge due to sheer fear.
The one responsible for this horrific tragedy…
The Demon King.
He was the true embodiment of terror.