The transition was never a clean break. For Shin, becoming Sung Byeon wasn't like stepping through a door; it was like being submerged in a vat of freezing, viscous ink. The memories of Min-ji—a woman he had never met, yet whose scent of jasmine and old paper lived in his nostrils—clashed violently with the cold, analytical data of his previous existence. He was a transmigrator, a cosmic anomaly tucked inside the skin of a nineteen-year-old boy.
As he walked toward the Ghost Library, the cobblestones felt unnervingly real. This world was a "fragile masterpiece." It lacked the screaming neon and orbital elevators of his home dimension, possessing instead a low-technology peace that felt like a curated museum exhibit. But the data stream in his mind was flickering. It was "corrupted," flashing images of a car crash, a hospital bed, and a flickering monitor showing a flatline.
Then, he saw the impossible.
Standing by the iron gates of the Ghost Library was a young man leaning against a stone pillar. He wore a designer jacket that looked too expensive for a student and had a smirk that suggested he had never faced a day of true consequence. He was the image in every mirror Shin had looked into for the past three days.
"Hey, Sung Byeon! Long time no see," the voice called out. It was a mirror image in sound, too—the same pitch, the same slight rasp.
Shin froze. His Helix Nebula eyes, usually a calm deep blue, began to swirl with violet light, a physical manifestation of his processing core overclocking. *I am in his body, but he is standing right there,* Shin thought. The logic circuits of his soul screamed "Error."
"You look like you've seen a ghost, buddy," the 'real' Sung Byeon laughed, pushing off the pillar. "Or maybe you just realized you're wearing my favorite shirt."
Shin didn't speak. He couldn't. This wasn't just a glitch in the world's "Source Code"; it was a full-scale paradox. If the soul of Shin inhabited the body of Sung Byeon, then who—or what—was standing ten feet away?
### The Sanctum of Whispers
They entered the Ghost Library together, a silent, tense procession. The library was an architectural marvel, its shelves rising so high they disappeared into a permanent layer of low-hanging mist. The air smelled of ozone and ancient parchment.
Shin ignored the doppelgänger for a moment, drawn to the section on **Astronomy and Astrophysics**. He needed anchors. He needed constants. He pulled a heavy, leather-bound volume from the shelf: *The Mechanics of the Heavens*.
As he turned the pages, he read about the **Great Oxidation Event**.
> "Approximately 2.4 billion years ago, a biological revolution changed the Earth's atmosphere forever. Cyanobacteria began producing oxygen, a gas that was toxic to the anaerobic life of the time. It was the world's first mass extinction—and its greatest rebirth."
>
Shin felt a resonance. He was the oxygen. This world was the anaerobic environment. His mere presence was changing the "atmosphere" of this reality.
"You're boring," the real Sung Byeon muttered, leaning over Shin's shoulder. "Why read about dead stars when there are girls and parties?"
"Because stars don't lie," Shin replied, his voice cold and resonant. "Physics is the only language that remains consistent, even in a world that allows two versions of the same man to exist."
"Whatever, 'Shin,'" the boy sneered. "You think you're so—"
The air in the library suddenly turned heavy. The mist at the ceiling curdled into a dark, oily smoke. Five shadows detached themselves from the architecture—**Interdimensional Rovers**. These weren't creatures of flesh; they were constructs of dark energy, hunters sent to prune anomalies from the timeline.
They didn't target the librarian, who had fainted behind her desk. They didn't target the books. They landed in a circle, their multi-jointed limbs clicking on the marble floor. Their sensors locked onto the two Sung Byeons.
"You've changed, 'Shin,'" the lead rover sneered, its voice a grating sound of metal on glass. It looked between the two. "One of you is a playboy—a useless remnant of a discarded timeline. The other is a corpse walking in a hero's skin. A transmigrator who shouldn't be here."
The lead rover's eyes glowed a sickly crimson. "Which one should I kill first to fix the equation?"
### Tectonic Shielding
The real Sung Byeon stumbled back, his face turning a ghostly white. "What are those things? Shin, do something!"
The lead rover didn't wait. It lunged, its arm elongating into a massive dark-energy blade. The strike was aimed at the "real" Sung Byeon's throat. It was a move designed to erase the original, leaving the "fake" Shin to collapse as his anchor to this world vanished.
Shin moved.
He didn't use magic. He didn't use a shield of light. He used the fundamental forces of the universe. As the blade descended, Shin reached out and grasped the air itself.
"Everything has a plus and a minus," Shin whispered. "You are a disturbance in the equation."
He didn't block the blade; he manipulated the **gravitational constant** in a three-inch radius around the point of impact. He increased the mass of the air molecules until they were as dense as lead, creating a localized "Tectonic Shield."
The dark-energy blade hit the invisible field. There was no clang of metal, only the sound of a structural failure. The blade shattered like glass against an immovable object. The rover recoiled, its limb vibrating from the kinetic feedback.
"Gravity is a bitch, isn't it?" Shin said, his eyes now glowing with the intensity of a dying star.
### The Planetary Fight
The other four rovers hissed, their bodies blurring as they prepared to warp space for a multi-directional strike. The library—the precious, quiet library—would be leveled if the fight continued here.
"We're taking this elsewhere," Shin declared.
He didn't run. He slammed his palm into the floor. Using the coordinates of the **Perihelion**—the point in an orbit closest to the sun—which he had just noted in the text, he folded the space-time fabric of the library.
In the blink of an eye, the library vanished.
The marble floor was replaced by scorched, red rock. The sky was no longer a vaulted ceiling but a terrifying expanse of crimson fire. They stood on a world caught in the final embrace of its parent star—a **Red Giant**.
The heat was a staggering **100°C** and climbing. The atmosphere was a thin, caustic haze of CO2.
"In this dimension, Earth is already dead," Shin told them. His voice didn't travel through the air—there wasn't enough oxygen to carry the waves. Instead, he projected his intent directly into their processing cores via mana. "Let's see how your dark energy fares against the **Inverse Square Law** of a dying star."
The rovers struggled. Their dark-energy forms began to bleed out, the intense radiation of the Red Giant stripping away their cohesive fields. The lead rover roared, a soundless vibration of rage.
"You think a little heat can stop us?" the rover projected. "We are the void!"
"The void is just an absence of matter," Shin countered, stepping forward. The heat didn't touch him; he was maintaining a localized cooling field by vibrating his own molecules at a frequency that canceled out the thermal energy. "But radiation... radiation is information. And this star has too much information for you to handle."
### The Finish: Singular Point
The five rovers gathered in a formation, their bodies merging into a single, hulking mass of shadow. They began to draw in the ambient heat of the planet, converting it into a "Dark Matter" blast. A sphere of pure annihilation began to form between their claws.
Shin didn't flinch. He didn't prepare a counter-blast. He simply held out his right hand, palm open.
"Applied Physics," he whispered.
He began to compress the air in front of his palm. He wasn't just squeezing it; he was folding it. He used his mana to mimic the conditions of the **Earth's core**—pressure so immense that atoms were forced into a state of degenerate matter.
He created a **Point of Singularity**.
It was a tiny, black bead, no larger than a marble, but it possessed the gravitational pull of a mountain.
The rovers' Dark Matter blast didn't fire. It couldn't. As soon as the Singularity formed, the dark energy was caught in its event horizon. The rovers screamed—a psychic wail that shook the very tectonic plates of the dying planet—as they were stretched like taffy toward Shin's hand.
"Spaghettification," Shin noted clinically. "A messy way to go, but mathematically inevitable."
The gravitational pull was so immense that the rovers were compressed into a microscopic speck. With a final flick of his wrist, Shin gave the singularity a nudge. Like a bullet fired from a railgun, the speck containing the five rovers shot away from the planet, spiraling into the sun's corona where they would be incinerated by fusion.
### The Return
The shift back to the library was instantaneous. The cool, ozone-scented air felt like a benediction.
The "real" Sung Byeon was collapsed against a bookshelf, gasping for air. He looked at Shin not as a friend, or even as a rival, but as a creature from a different tier of existence.
"Who... what are you?" the boy asked, his voice trembling.
Shin didn't answer immediately. He smoothed his shirt—the one the boy had claimed was his favorite—and adjusted his collar. The violet swirl in his eyes faded, returning to a calm, deep navy blue.
The librarian, having regained consciousness, peered over her desk. With shaking hands, she held out a plastic card.
"Your... your library card, sir," she stammered.
Shin walked over and took it with a polite nod.
"I'm just a student of the universe," Shin said, his voice now indistinguishable from the boy on the floor. He looked at his doppelgänger, a cold curiosity in his gaze. "And I think it's time I learned the 'Source Code' of why we both exist at the same time."
He turned and walked toward the exit, the weight of the book in his hand feeling heavier than the singularity he had just wielded. The "Mirror in the Library" had been shattered, but the pieces were beginning to show a very different picture of reality.