Ryu Saeyoung did not leave the infirmary for two days.
Kim Jisoo had half expected him to leap to his feet after waking, striding off with that kind of unstoppable determination the man radiated. But instead, Saeyoung had lain in the simple cot Jisoo set up in the corner of the lab, his body still stiff from whatever torturous journey had dragged him here. He ate little, spoke less, and mostly stared at the ceiling with a strange look—as if trying to remember whether he was still alive.
During those two days, Lee Hana hovered like a restless cat, both curious and annoyed. The System, of course, watched him without expression, as though cataloguing every breath. And Jisoo… Jisoo found himself glancing at Saeyoung more often than he wanted to admit, unsettled by the weight of the man's silence.
On the third morning, Saeyoung finally rose. He washed his face in the lab's sink, changed into the spare black clothes Jisoo had set aside, and approached him with steady, purposeful steps.
"I'm leaving," he said simply.
Jisoo, who had been calibrating one of his drones, froze and looked up. "Where?"
"To meet a scientist," Saeyoung replied. His tone was calm but carried a current of urgency beneath it. "The only one who has the knowledge to build what we need. My hope lies with him."
Jisoo's brows furrowed. "What are you planning?"
For the first time, Saeyoung's black eyes softened as he looked directly at him. "To create an energy barrier. One strong enough to protect this world."
The System's head tilted slightly at his words, its golden hair catching the sterile light of the lab. Lee Hana, perched on the desk beside Jisoo, leaned forward, her curiosity ignited.
"Energy barrier?" she asked. "From what?"
Saeyoung exhaled deeply. He seemed to choose his words carefully, as though the weight of what he was about to say could crush the room.
"There are entities out there," he began, "things that are not supposed to exist in this cycle of reality. They found Earth—your Earth. And they are trying to invade it… like a parasite."
The word sent a chill through the lab.
Jisoo's hands tightened unconsciously around the drone he held. "Invade Earth…?"
Saeyoung nodded. His expression grew grim, each word measured. "This planet, unlike many others, is protected by a massive energy barrier—the sun. The sun isn't just a star. It's a shield, radiating energy fields that keep outside entities from easily breaking through. For billions of years, that barrier has been enough. But the creatures who found Earth… they've discovered a way to weaken it."
The System's eyes flickered, the faint glow in its irises sharpening. "They've discovered a way to shield Earth from its own sun."
"Exactly," Saeyoung confirmed. "They're wrapping the planet in their own parasitic shroud. That's why the sunlight dims in your world. They're blocking Earth's natural barrier. Once that's gone… there will be nothing to stop them."
Silence blanketed the lab, heavy and suffocating.
Jisoo's breath hitched faintly. He remembered the endless dread in his previous life—the dimming of the sky, the monsters clawing through the streets, the feeling of suffocation in every breath. It had never been random. It had never been some natural catastrophe.
It had been them.
Entities from beyond, devouring worlds like carrion.
"…What are they called?" Hana's voice broke the silence, surprisingly steady for her age.
Saeyoung's eyes darkened. "The Fouls. That is the name given to them by scientists of the past world. They are corruption itself—things that cannot exist in harmony with life. They don't just invade. They infest. They overwrite worlds until nothing but themselves remain."
Even Hana, who often masked her fear behind stubbornness, paled slightly.
Jisoo clenched his jaw. "And you think… an energy barrier will stop them?"
Saeyoung nodded slowly. "It will. If we construct a barrier strong enough, we can repel their infestation and buy time. But…" His gaze hardened, shadows deepening in his eyes. "They will not stop. Once repelled, the Fouls will return. Stronger, hungrier, more desperate. The barrier may hold for a while, but not forever. When they return… we may have nothing left to fight them with."
The words landed like a stone in Jisoo's chest.
Time. That was all it would buy them. A reprieve, not a salvation.
Lee Hana crossed her arms tightly, her voice shaking despite her attempt to sound nonchalant. "So what—you're saying even if we fight them off, it's just delaying the inevitable?"
Saeyoung's silence was answer enough.
The System finally stepped forward, its childlike voice calm yet heavy. "That is why twelve Protectors and two Saviors were chosen. The barrier is only the first defense. To truly resist the Fouls, humanity must change. Adapt. The Protectors are the seeds. The Saviors… are the roots."
Hana groaned and threw herself back onto the desk. "There it is again, the school lecture tone. Roots, seeds, trunks. Next you'll tell me to photosynthesize."
But Jisoo wasn't listening to her. His sharp eyes remained locked on Saeyoung, voice steady. "Where is this scientist you're meeting?"
"Not far," Saeyoung said. "Two days' travel if I move quickly. He's been hiding, working in secrecy, because the Fouls' influence is spreading even now. He understands their nature better than anyone alive. If anyone can help us create the barrier, it's him."
Jisoo considered this in silence. He wanted to ask more—about how Saeyoung even knew of this man, about what cost building such a barrier would demand—but the mark on his palm still burned faintly. Haru's name.
The child who gave his life essence. The child who no longer existed.
If there was even the smallest chance to prevent this nightmare from returning, Jisoo couldn't dismiss it.
"…And if you fail?" he asked quietly.
Saeyoung's lips curved in a tired, humorless smile. "Then Earth will join the list of fallen branches. And Haru's sacrifice, your struggle, everything… will be for nothing."
The room fell still again, the weight of those words pressing down on them all.
Lee Hana's fists clenched on her knees. "Then don't fail," she said bluntly, her voice tight with fear hidden behind defiance. "Because I'm not ready to die yet."
The System tilted its head and gave her a faint, knowing smile. "That's the spirit of a Protector."
Kim Jisoo glanced once more at the glowing mark on his palm. His instincts screamed, as they always did, but this time not only of danger. They screamed of inevitability, of choices that could no longer be avoided.
Looking back at Saeyoung, his voice was low but steady. "Then go. Meet this scientist. Build the barrier. If that's the only chance, then we can't waste it."
Saeyoung's eyes softened slightly as he nodded. For just a moment, the burdened man seemed lighter—like seeing Jisoo alive had restored a sliver of his strength.
"I'll return," he promised. "And when I do… we'll make sure Haru's sacrifice wasn't in vain."
Jisoo said nothing, but his hand tightened into a fist around the mark.
That night, Saeyoung prepared to leave.
He packed light—only what he needed. His black coat, a few capsules of rations, a strange crystalline shard that pulsed faintly in the dark. Jisoo caught sight of it but said nothing. Everyone had their secrets.
As dawn's pale light broke through the reinforced shutters of the lab, Saeyoung stood at the entrance. Jisoo and Hana stood behind him, the System beside them like a quiet shadow.
"Two days," Saeyoung repeated. "If all goes well, I'll be back in four. Hold this place until then."
Jisoo gave a curt nod. Hana muttered something under her breath about "mysterious men disappearing like heroes in dramas." The System simply watched silently.
With one last look, Saeyoung turned and disappeared into the brightening world outside.
Kim Jisoo stared after him for a long while, the mark of Haru glowing faintly against his palm, before finally turning back inside.
The Fouls were coming. The sun was dimming.
Time was already running out.