The descent began with a single rusted fence.
Han pushed aside the warped metal sheet that partially covered the entrance. Behind it, a narrow concrete stairway dropped into darkness. Damp air wafted upward, heavy with dust and the faint scent of stagnant water.
Raon scanned the area one last time—the silent riverside, the broken bridge looming in the distance, the colourless sky stretching endlessly overhead.
It felt like the world was holding its breath.
"Here," Han whispered. "Follow me carefully. There's no light down there."
He flicked on a small flashlight he'd found in the mall earlier. The beam was weak, trembling slightly in his hand.
Raon stepped in behind him.
Every step downward made the sounds of the surface disappear—replaced by the low, echoing hum of air trapped under the river.
The walls were lined with maintenance pipes, chipped concrete, and markings left by workers long gone.
They were entering a tomb.
When they reached the bottom, the narrow stairway opened into a dim access corridor. Water dripped from pipes overhead, each drop echoing unnaturally loud.
Han pointed ahead.
"If this passage didn't collapse, it should connect to the Line 9 service tunnel."
Raon nodded quietly.
The two walked forward—slow, cautious steps. The sound of their shoes against the wet floor felt too loud, like it could summon something hidden in the dark.
Han's voice broke the silence.
"You know… I've taken this shortcut before," he said softly. "Sneaking to Seoul with friends, skipping school… never thought I'd be here again like this."
Raon walked a little ahead.
"Nothing is the same anymore."
"Yeah," Han murmured. "Tell me about it."
They turned a corner—and the corridor widened.
A faint, unnatural blue glow pulsed ahead.
Raon raised a hand, stopping Han.
"Don't move."
The two stood still.
The glow flickered, like the heartbeat of something alive.
Then—
Raon felt a cold sting at the back of his skull. A presence. Something watching from above—with curiosity… or hunger.
Han shivered. "D-Did you feel that?"
Raon didn't answer. His eyes remained fixed on the glowing light ahead.
The system message faded, but the feeling did not.
They resumed walking—closer, closer—until the source of the light came into view.
It wasn't a creature.
It wasn't a trap.
It was the collapsed entrance of the maintenance tunnel—its interior washed with a faint emergency light. Steel beams had fallen, but there was a narrow space they could crawl through.
Han crouched down. "Good. It didn't collapse completely. We can still get through."
Raon looked at the narrow opening.
Barely big enough for one person at a time.
Dark. Tight. Silent.
It was the only path.
"You first," Raon said.
Han nodded, lying flat to squeeze into the gap. His shoes scraped against broken concrete as he wiggled forward.
Raon waited until Han's legs disappeared into the darkness.
Then he crouched—
—but froze.
A sound echoed through the tunnel.
Not dripping water.
Not groaning metal.
A low… wet… dragging sound.
Slow. Rhythmic.
Something moving on the other side.
"H-Han," Raon whispered through the gap. "Don't move."
"What? Why—"
The dragging sound stopped.
Silence fell.
Raon held his breath.
Han held his.
The tunnel ahead seemed to tighten, the air thickening with an unseen tension.
Something was down there.
Under the river.
Waiting.
Raon narrowed his eyes, gripping the cold concrete.
The narrow passage spat them out into a world that should not have existed.
Raon emerged first, pushing aside the last slab of broken concrete. The faint flashlight glow revealed a vast, low corridor—wide enough to walk two abreast, with shallow water flowing endlessly through it.
Han slipped out behind him, splashing into the waist-deep water.
He gagged instantly.
"Urgh—what is this smell…? Are we in a sewer?"
Raon scanned the curved walls—metal girders exposed, pipes ruptured, debris piled along the sides.
"No," he answered quietly. "This wasn't a sewer before.
It became one after the collapse."
It made sense. The train route they intended to follow must have caved in, redirecting them into a damaged drainage tunnel beneath the Han River.
Water from above had poured in, mixing river water, sewage lines, and everything else swept in by destruction.
Their feet sank through sludge. Something soft brushed past Raon's leg.
He ignored it—but the hairs on his neck rose.
They switched on both flashlight and the small lantern taken from the mall. The lantern cast a dim circle around them, the water shimmering eerily.
As they moved deeper, the darkness pressed closer.
And Raon felt it.
A presence.
Not visual.
Not audible.
But there.
Following.
Watching.
Han trudged beside him, unaware. "Let's get through this quickly… it feels wrong here."
The deeper they went, the thicker the air grew.
And then—
A new smell.
Rot.
Decay.
Something long dead… and recently fed on.
"Stop," Raon whispered.
The lantern's glow touched something floating.
Bodies.
Dozens.
Fish bloated and torn open.
Strange river creatures with half-dissolved fins.
Human remains—some still clothed, others stripped to bone.
Han swallowed hard.
"T-they must've been swept in… after the bridge collapsed."
"No." Raon crouched beside a corpse.
"Look closer."
Han leaned in. The body's arm was missing from the elbow down. Deep crescent bite marks carved across the remaining bone.
"These weren't swept in," Raon said.
"They were hunted."
Han shivered violently.
Raon straightened, expression calm but voice hard.
"Open the Shop."
Han blinked. "W-what?"
"You can't fight barehanded. Use your coins. Buy a weapon. Increase your stats if possible."
Han stared at him with a strange mixture of fear and trust—then opened his interface.
Blue light reflected in the water.
Raon did the same.
He purchased:
—A standard iron sword.
—A compact Sphere Light (F-Rank): Creates a floating orb of illumination for 60 minutes.
—A minor stat boost in Agility.
Han bought a cheap longsword and a utility flare that could light up a small area.
Raon flicked his thumb against the Sphere Light—
A small sphere rose from his palm, hovering in the air before blooming into a bright, white radiance.
The tunnel lit up to forty meters in every direction.
And that's when they realized the horror:
The bodies continued.
Piled along the walls.
Dragged into corners.
Something had been eating here regularly.
They pressed forward, following the flow of water until the tunnel opened into a massive underground junction.
Four paths.
Front, left, right, and the one behind them.
A crossroads beneath the river.
Han lifted his light. "Which way—"
A wet scrape echoed behind him.
Raon turned just as something lunged out of the water.
"Han—move!"
Han twisted but too late—the creature latched onto his shoulder, dragging him backward with a guttural hiss.
Raon's sword flashed through the air—
SHLICK—cleaving the creature's neck. Its body hit the water with a splash.
Han staggered back, breathing hard. "T-thank you—"
Another screech—this time from the left passage.
Followed by another from the right.
Then another.
They emerged from all three directions
crawling from water, from ceilings, from the shadows. Pale, eyeless things with elongated jaws and limbs built for the dark.
Han raised his sword in panic. "What—what are these!?"
Raon didn't answer.
He activated the Sphere Light fully.
The orb brightened to near-daylight, flooding the chamber with stark illumination.
The creatures recoiled—then shrieked louder, enraged.
"Fight!" Raon shouted.
The first creature lunged. Raon sidestepped and struck its head, sending it collapsing into the water. Han managed to stab another, though his hands trembled violently.
But for every monster they killed—Three more crawled out from the dark.
The sphere of light reflected off dozens of slick bodies. The walls seemed to move as the creatures climbed over each other.
Han's voice cracked in terror.
"Raon—we can't—we can't keep this up!"
"I know that."
The sword grew heavier in Raon's hand. His breath came out ragged.
The monsters kept coming.
"We have to run," Raon said sharply.
"Pick any path—we just have to get out."
Han nodded frantically.
But the creatures were closing the circle around them.
And only one of the four tunnels was not yet blocked.
Raon grabbed Han's wrist.
"Left! Run!"
They splashed into the left passage, chased by dozens of shrieking, blind creatures that rushed toward the fading light—
And the river swallowed their footsteps