Prologue — The Broken Cogwheel
The appearance of Curse turned every common sense in the world upside down in a single instant. And what he brought with him were beings entirely unlike humanity — creatures bearing horns and wings, endowed with physical abilities far beyond any human, wielding technology and powers that this world's science could not begin to explain.
People came to call them Demons.
Naturally, the world descended into chaos. Beings of unknown origin from another world. A Demon King of overwhelming power. And the countless demons who followed him. Nations mobilized their armies, and humanity braced itself for war.
But contrary to all expectations, Curse did not want a war.
He spoke quietly before the representatives of every nation: their world was already gone. There was nothing left to return to. All they wanted was to live quietly in this one.
And then he made a single proposal. They would found a nation of their own — for themselves and their demons — upon some suitable stretch of open sea. If humanity granted them that, they would contribute their technology and resources to this world in return.
At first, no one believed a word of it. But as time passed, the nations came to understand exactly what he was offering. Technology humanity's own science could never hope to match. Materials that had never existed before. Knowledge capable of dragging the entire world's development centuries ahead of schedule.
Endless debate followed. Wariness and suspicion collided with national interest after national interest. Even so, after long and grueling negotiations, humanity chose to accept them — and gave them a new name.
Visitors.
Beings who had arrived from another world. And who would now live on as members of this one.
Thus was forged an imperfect but peaceful coexistence between humans and demons. Little by little, people grew accustomed to their presence. Shops run by demons began to appear. Humans and demons started working side by side. Children no longer flinched in fear at the sight of a demon's face.
It seemed as though the world was stepping into a new era.
Then, before long, another problem began.
Strange phenomena started occurring all across the globe. Cracks split open across the sky and the ground, and from beyond those fissures, something emerged.
It was another Gate.
What it was. Where it came from. Who — or what — had created it. No one knew. Only one thing was certain: the beings that poured out of these Gates bore no resemblance whatsoever to Curse and his demons.
They could not understand human language. Negotiation was useless. So was fear. So was mercy. So was any emotion at all. They existed for one purpose alone — to attack and kill the living things before them. Nothing more.
Humanity gave them a name as well.
Monsters.
At first, most of them were foes that human strength alone could handle. When the army moved, they could be exterminated. But as time went on, the situation changed. Monsters that ordinary weapons could not so much as scratch. Monsters that took to the sky and rained destruction upon cities. And eventually, monstrosities capable of wiping an entire city off the map in a single blow began to appear all over the world.
Countless lives were lost. Countless cities were destroyed. Humanity was pushed steadily back.
It was the demons who extended a hand. Curse and his people used their power and technology to aid humanity — analyzing the Gates, researching the monsters, developing new weapons, and even joining the exterminations directly. Thanks to their help, humanity barely managed to hold the line.
But that, too, did not last.
The monsters only grew stronger. More powerful individuals emerged, more dangerous Gates opened, and no matter how much the demons contributed, they could not defend everywhere at once. The limits were drawing near.
And time flowed on... to roughly nine years before the present day.
Humanity still did not know. It did not know what the true threat awaiting them would be.
Nor did it know that before long, a boy would meet a girl. That this meeting would shake demons and humans alike, Gates and monsters alike — and the very fate of this world.
This is the story of a boy who met a girl and changed the world.
And...
...the story of how that boy was destroyed as a calamity.
In a remote corner of the city, in an alley where few footsteps ever wandered, a small café sat tucked away. It was still early in the morning, but inside, preparations for opening were already in full swing. A black-haired woman hummed a tune under her breath as she wiped down tables, straightened chairs, and tidied the display case, her face brimming with a bright, energetic smile.
And behind her stood a black-haired boy, his face scrunched up in disgust, both arms loaded with garbage bags.
"Noona. You seriously want me to throw out all of this?"
The boy's name was Rai Hopeless — the younger brother of Ragna Hopeless, the owner of this café.
Ragna turned around and flashed him a beaming grin.
"What kind of man can't handle a little trash?"
Rai's face twisted even further. "And you call that an answer?" He heaved up the bags in both hands. "'It's the weekend, so let's make him do all the work'—"
Ragna just laughed, completely unbothered. "If you don't like it, skip breakfast~!"
"You're the worst, you know that?"
Grumbling all the while, Rai finally trudged out of the café.
Ding-a-ling~!
He pushed the door open and stepped out onto the street, the garbage bags still hanging heavy from his hands.
"Rai~~!!" Ragna hollered from inside the café. "Bring back more trash bags on your way!"
"Yeah, yeah. Got it."
Rai answered half-heartedly and started down the alley.
Rai was fifteen now. He had no immediate family — he'd lost them all in a gate accident when he was barely a newborn. After that day, only one person remained to him: his cousin, eight years his senior.
Ragna Hopeless. To Rai, she was both an older sister and the only family he had left. The two of them had lived together ever since leaving the orphanage. Money had never been plentiful, but Ragna had somehow scraped by running this café and raising him, and Rai had grown used to grumbling at her every step of the way while never once leaving her side.
It was an ordinary life. At least, it had been right up until this morning.
"Haaah..." Rai let out a long sigh. It was the weekend, and all he wanted was to crawl back into bed. The garbage bags swinging from his hands were a constant irritation.
"If I dump these and head back..." His footsteps slowed. "...why can't I just sneak a nap at home?"
He deliberated for a moment — then happened to glance ahead of him.
"Huh?"
His footsteps stopped. Rai blinked. Then rubbed his eyes.
"What the...?"
Something was floating in front of him. In the empty air, a translucent window hung suspended — as if it had appeared for his eyes alone. And across its surface sprawled rows of characters he could not read at all.
"........?!"
Rai stood staring blankly at it for a long while. "What is this thing?" He tilted his head to the right. Then to the left. The window didn't budge.
He carefully reached out a hand. "It's... actually there?"
Vmmm.
"Hold on... am I hallucinating right now?"
Rai's face slowly stiffened. "I slept fine, though." He'd woken up perfectly healthy that morning and had come out to dump the trash, nothing more. And now a window of unknown origin was hanging right in front of his face.
What made it even more absurd was the writing inside. "I can't understand a single word of this...?" He squinted hard at the window. The characters definitely looked like writing — but they matched no language he knew. He couldn't even begin to pronounce them.
Strangely enough, though, the two buttons at the bottom corners of the window somehow made intuitive sense to him.
Left. And right.
Rai's gaze flicked back and forth between them. "So this one's accept..." His finger drifted to the opposite button. "...and this one's decline?" He couldn't have explained why. It just felt that way, inexplicably.
A flustered look crossed his face. "Well... whatever. It's weird that it's just floating here anyway." Rai scratched his head. "If I just press something, it'll go away, right?"
He mulled it over for a moment. Then, without giving it any real thought, he reached out. His finger came to rest on the button that seemed to say accept.
Click.
In that instant —
The world stopped. The wind died. The passersby froze mid-step. The rumble of cars, the cries of birds — everything cut out at once.
Rai's eyes flew wide open. "What—"
The window floating in the air began to glow. And then the world began to move again — but it had started to change, warping into something that no longer quite resembled the world Rai knew.
The one careless choice a boy made that day would completely overturn the fate of the world.
FWOOSH.
"Huh?" Rai lifted his head at the sound from above. "What the... up there—"
A blue-light figure was plummeting out of the sky. Rai's jaw hit the floor.
"Th-that's a person---!!!"
THUD--!!
He flung the garbage bags aside and bolted.
Ta-da-da-da-da-da-da-da--!!!
"Are you kidding me...!! Why is a person falling out of the sk—"
Vmmm. Vmmm.
"Uh..."
Lying there was a girl of unknown origin.