The year is 2025 AD. International Space Station.
"Tridid... tridid... tridid... cklunk," a hand slapped the analog alarm clock on the table.
"Ugh."
An astronaut woke up, sat up in his bunk, and looked out the window. He saw the blue planet, which felt close enough to touch. Then his eyes drifted back to the alarm clock he had just silenced.
"Ah, morning already," he muttered.
He got out of his bunk. His feet didn't touch the floor as he floated, so he grabbed his boots and put them on. "Csss," his feet connected with the floor as soon as he put on his gravity boots. He unbuckled the straps that held him in bed and stood up, stretching.
After that, he casually floated out of the room and down a rotating hallway toward the cockpit. Once there, he sat down, grabbed a tablet, and started swiping the screen. In front of him, he had a clear view of Earth and the sun from a distance.
"Just another normal morning," he said, typing.
But, "grrrk... greeek," he felt the space station shake. The astronaut immediately put down his tablet and stared ahead, his eyes wide as a white, swirling vortex opened up in the vacuum of space right in front of the Earth. The point grew bigger than the Earth itself, becoming blinding and awesome yet terrifying.
"Huh, what is that?" he asked himself.
He unbuckled his boots and floated closer to the cockpit window. "Grrrrrrk," the shaking inside the station got more intense. The space station felt like it was in an earthquake. The astronaut's eyes widened, seeing a phenomenon that looked similar to a black hole billions of light-years away, but what was in front of him was a white hole, spewing out countless celestial objects.
"I have to contact headquarters," the astronaut muttered.
He immediately floated over to the communication console behind the pilot's seat. Without a moment's delay, he sat down, pushed some buttons, and pulled the mic closer.
"Houston, copy... Houston... come in, Houston."
"Teet... teet... teet," the alarm blared, and the shaking got worse. The astronaut turned to look forward, his eyes wide again. "Klotak," he dropped the mic, mesmerized by the strange phenomenon in front of him.
Slowly, a round, planet-like object, exactly the same size as Earth and colored blue, emerged from the white hole, sending a shiver down the astronaut's spine. The shaking in the space station became violent, forcing the astronaut to hold on to his seat to keep from being thrown. He turned back to grab his mic, not understanding what was happening in front of him and panicking, as this phenomenon was definitely not in his training manual.
"Houston... come in, Houston!" he yelled in a panic.
The astronaut's eyes followed the Earth-like planet as it fully emerged. The space station was now positioned between the two blue planets, which faced each other. The white hole disappeared, but the Earth-like planet continued to move slowly toward the original Earth.
"Oh no... that planet is going to hit Earth," he thought.
The astronaut's fears were realized. "Grrrrrrrrrrk," the space station shook violently. The astronaut kept trying to contact headquarters, his eyes glued to the Earth-like planet approaching his station. Finally, as the space station was pulled in by the approaching planet's gravity and began to enter its atmosphere, "grrrrrrrrrrrrrk... grrrrk," the entire space station shook violently and began to burn up as it entered the atmosphere.
The astronaut, seeing what was happening, covered his face with his arms and screamed in a panic, unable to do anything.
"Aaaaaaaaaaaaa!"
"Blarrr," the space station was instantly incinerated, reduced to nothing in the atmosphere of the blue planet that looked exactly like Earth. After that, the Earth-like planet began to touch the original Earth, but instead of colliding, they merged. When the two blue planets completely merged, the new, unified Earth gave off a bright light, and "blam," a massive ring-like wave rippled through space, as if to signal that all of reality had changed.
***
The whole world descended into chaos. Many cities and even entire countries vanished as dungeon portals opened, releasing monsters beyond human comprehension, which were previously only thought to exist in legends or stories. Of course, these creatures couldn't be fought with regular firearms; even a nuclear bomb could only kill half of them, but at the enormous cost of destroying the country or city it was dropped on repeatedly.
After 10 years of fighting and losing nearly half of the total human population, scientists discovered a change in the human body. Ghost particles, also known as neutrinos, which had been difficult to study because they passed through matter like ghosts, were now sticking to the human body. This gave humans all kinds of superpowers, depending on their body's absorption, but not all humans were blessed with this gift.
The humans who possessed these magical-like superpowers began clearing the monsters that roamed outside the dungeons and closing the dungeons with their powers and weapons made from neutrinos, which also got stuck in stones and other solid objects. These objects were called nether materials. In a short amount of time, they successfully defeated the roaming enemies and closed almost all the dungeon portals, but with a great deal of sacrifice.
Humans without powers helped rebuild life back to normal under the guidance of the UN, which had changed its name to the Nation of Humanity, or NOH. It became the only remaining country in the world, though it still contained the flags of the USA, China, Russia, United Kingdom, Germany, Japan, North Korea, South Korea, and a few other remaining powerful nations.
These super-powered humans were named Chasers and were governed by an association under the NOH called the Chasers Association, or CA. Life began to return to normal, although dungeon portals would still suddenly open in the capital of Neopolis, a city previously known as New York, where the UN headquarters was located in the Turtle Bay area of Manhattan.
But because more and more people became Chasers and passed the association's tests, the world finally entered a truly new normal. The sudden appearance of dungeon portals was just a part of this new life, though scientists continued to investigate what the dungeons really were and the purpose behind their appearance in this world. Now, dungeons were even used as a benchmark for Chasers who wanted to test their strength or show off for fame.