The Black Crystal
After the hunt, the silence on the third floor lingered long after the fighting stopped. When a space that had been filled with blood, gunfire, and explosions suddenly grew too quiet, other sounds became unnaturally loud. The soft whir of the barrier equipment powering down, the crackle of voices over the radio. Ha Yul held her karambit loosely. Strength still lingered in her fingertips, but her body carried the aftershocks of the recent engagement. The heightened senses that always followed a hunt. Familiar, yet never comfortable. At times like this, the scent of blood grew sweeter and thicker, and the sensation of tearing flesh lingered on her hands.
Yu-jin was the same. The residual heat from using Blood Qi had not yet fully subsided. With every beat of her heart, the warmth spread along her blood vessels to the very ends of her nerves. Old texts called this state "Qi boiling," but modern researchers used colder, more clinical terms. Blood Qi was a bio-active energy that coursed through blood and the nervous system. The heart was the pump that drove it, and the nerves were the circuits that directed it. Anger drew it upward, fear sent it into overdrive. Excitement accelerated its flow, and only by regaining composure could the current return to its proper course. That was why martial artists were dangerous right after a hunt. Their bodies had not yet accepted that the battle was over.
"Stay still."
Yet Yu-jin's voice beside her remained unchanged. As expected of a Peak Master who had reached the wall of the absolute peak, she could control herself to a degree. It was different for Ha Yul, who had only trained in external arts and was merely an intermediate-level expert. Before Ha Yul could even turn her head, Yu-jin grabbed her wrist with a gloved hand. Normally she would have reflexively shaken it off, but Ha Yul stayed still because it was Yu-jin. With her other hand, Yu-jin pulled a piece of gauze from an inner pocket of her combat uniform and silently wiped the blood spattered on the inside of Ha Yul's wrist. The dark red stain seeped into the white gauze. Ha Yul glanced down at the touch for a moment.
"It's not my blood."
"I know." Yu-jin answered briefly, then wiped the remaining bloodstain on her wrist once more. Then she lifted her gaze to Ha Yul's cheek. "There's some there too."
Blood from the fight must have grazed her. Yu-jin folded the gauze to a cleaner side and wiped Ha Yul's cheek once. Even through the glove, the touch felt strangely warm. Ha Yul let out a small laugh.
"Team Leader, do you do this kind of thing on-site too?"
Yu-jin folded the bloodied gauze and replied, "Only if you stand there without lifting a finger."
"Were you worried?"
Yu-jin spoke calmly. "Because you still haven't broken the habit of thinking 'as long as I don't die, it's fine.'"
Ha Yul did not answer. Yu-jin did not say anything more either. Like someone who knew that prolonging the conversation would turn it into something other than on-site talk, she withdrew her hand and turned her gaze toward the corpse. Yu-jin crouched in front of the body.
"Flip it."
Ha Yul silently pushed the mutant's shoulder with her toe, turning the body slightly. One of the team members secured the corpse with a long hook-shaped tool. The mutant's neck was half-bent because Ha Yul had torn it out at the end. At the edge of the wound, traces of regeneration that had stopped mid-process clung like jelly. For an ordinary rampaging mutant, regeneration would not continue this long after death. Regeneration was not a miracle that made flesh reattach on its own. The corpse before them had imitated that process for a short while even after its heart had stopped. Someone had implanted a power in this mutant's body that was different from normal circulation—filthy and unstable.
Yu-jin carefully lifted the torn flesh inside the neck with the tip of her blade. At first, only blood and shredded muscle were visible. But deeper, between the dark red tissues near the cervical vertebrae, an odd glint caught her eye. It was not the color of natural bone or blood clots. It was too dark, too smoothly glossy. Yu-jin's gaze turned cold.
"Light."
A team member immediately shone a light. When the beam reached deep inside the neck, the object became clearer. A black crystal fragment about the size of the first joint of a thumb. Fine red cracks spread across its surface like a spiderweb, and the surrounding blood vessels and nerve tissue clung to it as if they had taken root. It was an artificial foreign object that had been forcibly implanted, yet it had also become part of the body—an unpleasant fusion.
Ha Yul muttered, "It's not a blood pill. It's a blood crystal."
Instead of answering, Yu-jin prodded the tissue around the crystal with her blade. At that moment, the muscles inside the already-dead corpse's neck twitched faintly. One team member reflexively aimed a gun, but it was only a residual reaction. A very weak pulse passed across the crystal's surface once, then stopped.
"Does it react when touched?" a team member in the rear asked quietly.
"They must have channeled all their Blood Qi into this," Yu-jin said calmly. "That's why it could still react even after the heart stopped."
Ha Yul also crouched down and looked at the black fragment. Blood pills grew inside the body. They formed when blood flow, nerves, breathing, and emotions remained stably aligned over a long period of training—a controllable core of Blood Qi. Their color was red, and they hardened according to the practitioner's level. Blood crystals, on the other hand, were different. They formed when Blood Qi decayed and twisted, then solidified. Created through mutation or drugs, they were black, murky, and sharp.
"If it's black, it's almost certain," Ha Yul said quietly.
Yu-jin pointed with her blade at the side of the cervical vertebrae. "The placement is vicious too."
Ha Yul nodded. Anyone could see this had not formed naturally—it had been artificially implanted. Blood Qi flowed with the blood and spread along the nerves. The cervical vertebrae housed the spinal cord and major nerve bundles. Implanting a blood crystal right in the center of that—
"It forced the entire body into a rampage," Ha Yul said.
Yu-jin's gaze swept over the corpse. "The more its strength and regeneration increased, the more it must have damaged the mind."
Ha Yul looked down at the corpse's jawline. "Nothing's better for accelerating monsterization."
Just before dying, the monster had uttered a few human words. The voice was too clear for a fully bestial mutant, yet too clumsy for a normal human. That ambiguous boundary was all the more ominous. Emotion and Blood Qi were connected. Fear sent Blood Qi into overdrive, excitement accelerated circulation, and losing control meant the end. Someone had likely kept stimulating and driving this mutant, boiling its internal Blood Qi beyond its limits, then implanted the blood crystal into its cervical vertebrae in that state.
Both of their gazes turned to the ceiling at the same time. The words the corpse had left just before dying felt real once more. Yu-jin stood up and gave orders immediately.
"Expand the search range to the upper floors." She spoke briefly and clearly into the radio. "Confirmed artificial implanted blood crystal in the third-floor mutant's corpse. Natural rampage is no longer possible. There's a high probability of other mutants in this building, so everyone stay alert."
The team moved again. They decided not to extract the blood crystal on-site immediately, but to preserve it along with the surrounding tissue. Evidence like this did not end with simply removing the crystal. They had to examine the insertion angle, the range of nerve invasion, and the state of vascular adhesion. How the artificially created blood crystal had been made to settle inside the body, what reaction the victim had shown—those answers would remain inside the body.
Ha Yul stopped beside a pillar near the ceiling. "Here."
Yu-jin and two team members approached at once. The concrete surface climbing the pillar toward the ceiling bore several long gouges. Claw marks from something that had climbed up with force. At the end was a half-open ventilation duct cover in the corner of the ceiling. It had not been unscrewed—the cover had been pried open from inside, one side bent upward. Black blood and scratch marks stretched long into the duct entrance. Something had gone inside. And crawled upward.
Yu-jin said, "Did it escape?"
Ha Yul looked up at the duct entrance and answered, "No. It went up."
Escape and ascent were different. If the mutant that had just died was a failed experiment that had fallen midway, then the remaining one had likely succeeded in going higher. Yu-jin made her decision at once.
"We'll check the duct. It's narrow, so only two people go in." She glanced at Ha Yul and added, "You and me."
A team member reacted immediately. "Team Leader, we should secure visibility inside first—"
"Wait outside." Yu-jin cut her off. "If I need company, I need someone who can find the way inside the duct."
That someone was Ha Yul. When it came to this kind of tracking, Ha Yul was far more sensitive. The duct entrance was just narrow enough for one adult to crawl through. Inside was dark and cramped, filled with the smell of old dust mixed with metal and, deeper in, a fishy odor. When Ha Yul caught that scent, her eyes narrowed slightly.
"It's in there."
"Alive?"
Ha Yul spoke shortly. "It's already dead…… but it feels empty."
Some corpses could be identified by smell alone. Whether the entrails had been torn out, whether they were intact. Flesh, blood, organs, and bodily fluids rotted at different speeds and in different ways. Yet the smell coming from deeper inside, though clearly that of a human corpse, felt strangely light, as if the inside were hollow.
The two entered the duct one after another. The inner walls were streaked with bloodstains and sticky bodily fluids, and at several points the metal looked as though something had twisted its body forcefully while passing through. They had not gone far when Ha Yul raised her hand in a stop signal. At the edge of the flashlight's beam, something was caught. At first it looked like clothing tangled inside the duct. But when she changed the angle of the light, a human arm came into view. A corpse. It was wedged, twisted, at a square junction where the duct widened slightly. As they drew closer and shone the light, the full picture emerged. It appeared to be an adult male. He wore work clothes, and a redevelopment site access card still hung half-torn from his chest. His face was frozen in an expression of surprise. And—his abdomen was completely caved in. It looked as though everything inside had been removed and the skin roughly patched back together. Where the belly should have bulged, it sagged, and the line from below the ribs to the pelvis resembled the folds of empty leather rather than the three-dimensional shape of a human body.
When Yu-jin carefully lifted the hem of his clothes with a gloved hand, an even more horrific truth appeared. The abdomen was not open. On the surface it looked intact, yet there was nothing inside. Instead of the resistance of organs that should have been felt beneath the skin, there was only a soft, light, shell-like sensation. An abnormal emptiness could be felt between the ribs as well. It was as if the lungs, heart, stomach, intestines, and even the major blood vessels had all been sucked out, pulled free, or replaced by something else and then vanished.
Ha Yul's gaze turned cold. "It wasn't eaten."
Yu-jin asked quietly, "Then?"
"It was harvested."
Beasts usually tore and ate. Starving mutants did the same. They ripped, chewed, spilled, and left remains. But this? The flesh was not scattered messily, and only the insides had been selectively taken. This was not the work of a mutant. It was human.
"It might have been used as material for artificial blood crystal production." To create blood crystals outside the body rather than inside, one would ultimately have to grind up humans. Yu-jin examined the corpse's neck. Small puncture marks similar to injection sites remained there as well. Whether they were from before or after death could not yet be determined.
At that moment, a very faint sound came from deeper inside the duct. The sound of metal being pressed once with a squeak. Both of their gazes turned at the same time. Yu-jin placed her hand on her sword hilt, and Ha Yul gripped her karambit again. Fighting inside a narrow duct was the worst. Posture, visibility, and above all, no room to evade. But they could not retreat now either. If they turned back here, whatever had gone up would hide even deeper. Ha Yul spoke very quietly.
"It's still up there."
Yu-jin answered in the same tone. "I heard."
The flashlight beam was still narrow, and the darkness beyond that narrow light still hid many things. The hunt that had not ended, now shifted upward. They had only just found the entrance to some experiment that implanted artificial blood crystals and emptied people's insides while sending something to the upper floors.