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The maintenance workshop on Level B2 of Jongno 3-ga Station smelled of industrial cutting fluid, oxidized copper, and scorched sugar.
On the long steel workbench, lit by a single battery-powered fluorescent tube, sat six empty aluminum tea tins. Beside them lay a pile of white powder scooped from fifty-pound sacks of lawn fertilizer found in the subway mall's garden display, mixed three-to-two with granulated sugar from the station breakroom.
Kael stood over the bench with a wooden spatula, carefully stirring the dry mixture in a stainless steel pot resting on a small propane camping stove. The heat was kept low. Too much flame, and the potassium nitrate would ignite early, burning the workshop to a cinder; just enough heat, and the sugar melted into a thick, golden caramel that bound the nitrate into a dense, slow-burning smoke compound.
"Keep the temperature under two hundred degrees," Kael said without looking up. His voice was steady, rhythmic, matching the slow, circular motion of his hand. "If it starts turning dark brown, pull the flame immediately. You want a heavy caramelization, not a fire."
Min-Jae sat on an overturned tool chest three feet away, watching Kael's hands with intense focus. "How long does a tin burn?"
"Forty-five seconds," Kael replied. "It doesn't explode. It vents through three quarter-inch holes drilled into the top lid. It generates a cloud of thick, white, potassium-rich smoke that fills an underground parking bay in eight seconds. It strips sightlines, burns the eyes of anyone without goggles, and suffocates a rifleman's line of fire before he can aim down his receiver."
Sergeant Kwon was sitting on a metal stool across the bench, using a small brass file to clean the firing pin of his Daewoo K2 rifle. The dry *rasp-rasp-rasp* of the file against metal provided a rhythmic counterpoint to the bubbling caramel.
"Old insurgent trick," Kwon noted, a faint, approving grunt in his chest. "We pulled three of these out of a bunker near the DMZ back in '14. Crude, but effective in enclosed spaces."
"It's not a trick; it's basic chemical utility," Kael said. He turned off the propane valve, reached for a pair of thick leather welding gloves, and began spooning the molten golden paste into the six aluminum tins, pressing a length of slow-burning cotton fuse—soaked in saltpeter and dried—into the center of each tin before sealing the lids with duct tape.
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When the tins were set aside to cool, Kael stepped back from the bench and looked at Min-Jae.
"Take the shotgun," Kael ordered.
Min-Jae stood up immediately, picking up the 12-gauge pump-action from the workbench. He checked the action—breech open, magazine tube clear—before letting the bolt slide home with a crisp, metallic *clack*.
"Show me your room-clearing pivot," Kael said. "Target is six feet past the doorframe on your left."
Min-Jae took a low, balanced stance. His fast-twitch muscles—accelerated by the Amber core integrated into his legs—fired instantly. He snapped his body ninety degrees to the left, bringing the shotgun receiver up toward his cheek in a blur of movement.
*Thud.*
His left elbow hit the corner of a steel storage locker, the metal barrel swinging wildly two inches past the intended target line before he managed to drag the sights back into alignment.
"Too fast, sloppy footwork," Kael stated coldly.
Min-Jae lowered the weapon, his jaw tightening as he looked at his bruised elbow. "My feet moved before my hips rotated, Hyung. The Amber energy... it feels like my legs are trying to leap before my upper body catches up."
"Because you're letting the fast-twitch acceleration run your body instead of using it to anchor your stance," Kael explained. He stepped forward, grabbing the barrel of the shotgun with his left hand and forcing it down.
"Fast-twitch speed isn't about moving like a runaway train," Kael said, looking directly into the boy's golden-ringed pupils. "It's about shortening the time between decision and execution. When you enter a room, your lead foot doesn't sprint. Your lead heel plants hard, your hips drop two inches to lower your center of gravity, and your core muscles pull the barrel into alignment with your eyes."
Kael demonstrated without a weapon. He stepped forward—a short, explosive, low-slung movement that covered four feet in a fraction of a second—and came to a complete, rock-solid halt with his hands low, his frame entirely stable, ready to absorb recoil or pivot ninety degrees in either direction.
"You don't chase the target with the barrel," Kael continued. "You turn your entire torso like a turret. If your feet are planted wide, the gun is already pointed where your eyes are looking."
Min-Jae absorbed the correction. He closed his eyes, took a deep breath through his nose, and reset his stance.
*Inhale. Exhale.*
He opened his eyes, dropped his center of gravity two inches, and pivoted.
*WHOOSH.*
This time, there was no clatter against the storage locker. His lead heel planted into the concrete floor with a dull, heavy *thud*, his hips turning smoothly, bringing the shotgun up in a tight, three-foot arc that stopped precisely on the center of the doorway. The barrel didn't waver by a millimeter.
"Better," Kael acknowledged quietly. "Again. Ten times. If your foot slips on the grease, you do ten more."
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By eleven o'clock, the autumn storm outside had turned into a steady, torrential downpour.
In the medical alcove on Level B1, Yuna was packing the final trauma kits. She handed Kael three small, rubber-stoppered glass vials containing a clear, slightly iridescent solution.
"Diluted Cyan extract," Yuna said as Kael carefully stowed the vials in the padded loops of his tactical vest. "If anyone takes a deep laceration or a bullet graze, crack the seal and pour it directly into the open wound before applying the pressure dressing. It will jump-start localized vascular clotting and prevent hemorrhagic shock for twenty minutes."
"Understood," Kael said. He checked his utility belt: two smoke tins in his left pouch, his carbon-steel tanto on his right hip, his secondary drop-point knife at the small of his back, and two spare 12-gauge buckshot hulls in his vest pockets.
Kwon stepped up to the table, slinging a three-foot pair of heavy steel bolt cutters over his shoulder alongside his K2 rifle. His face was set in hard, experienced lines.
"The secondary service line beneath Jongno Avenue is flooded ankle-deep," Kwon reported. "It's cold, wet, and miserable. Perfect weather for a breach. Kang's sentries on the upper ramp will be huddled under blue tarps trying to keep their cigarettes dry."
"Keep your ear canals clear until we reach the riser," Kael reminded the group. "No wax for the approach—we need full auditory processing to track surface Skimmers while we're in the culvert. Wax goes in three minutes before we breach the B2 parking bay."
Min-Jae adjusted his school blazer over his shoulder rig, his six-inch combat knife resting securely against his left ribcage, the shotgun held low under his right arm. "I'm ready, Hyung."
Kael looked at the small group—three people who had started this week as strangers in a collapsing world, now standing in a dark subway basement bound by necessity, discipline, and the cold reality of survival.
"Jin-Hyuk is locking the Level B1 fire gates behind us," Kael said. "If we aren't back by three in the morning, the north corridor is welded shut. We don't get trapped in that garage, and we don't leave wounded behind. Move out."
They pushed through the heavy rubber curtains of the maintenance bay and stepped into the pitch-black utility tunnel, heading north toward Gwanghwamun into the cold, rushing dark.