Black light was swallowing the village. The sensation of thought capacity returning was like the moment a face breaks the surface of water. A sudden rush, all at once. But immediately after, exhaustion crashed over her entire body. Even while restrained, her body had been pushed to its limits. The strain of mental scanning, sleepless nights, overwork piling up—the baseline of a body on the verge of collapse. Now, with the "lid" of syntactic restraint removed, all of it came due as a single invoice. Her knees were trembling. She could barely stand. But the north was black. Houses. Fields. Stone walls. The northern half of the village was slowly dissolving into black light. Erosion—an erosion. The wave of collapse leaking from where the seal of Nox Regalia had come undone. To Yui's eyes, the syntactic structure was visible. A memory leak. Asynchronous errors cascading from the source. She knew where to stop it. If she got close and inserted a debug, she could push it back locally. The problem was that her thought capacity was less than half. "I understand that stopping the root is necessary," Seto Yui said as she ran. Ratharis was beside her. The first prince, who should have become a violator of royal orders from this very moment, ran alongside her without a word. "I'm heading to the source. But before that—" Seto Yui said. She deployed a debug. Strings of light spread from her fingertips, inserted into the black wave before her eyes. There was resistance. She pushed back. The black light, roughly three meters in diameter, retreated by a single step. "—This is a patch. Emergency treatment," Seto Yui said. "I understand," Ratharis Ordina replied. His answer was brief. Ratharis, sword still drawn, slashed at something mutated seeping from the edge of the erosion beside Yui—what had once been a small animal, its form collapsed and consumed by black light. A single flash, soundless. Yui moved to the next erosion point. She placed her hand. Inserted the debug. It retreated. Then the next. (I can't physically handle all of them.) She was calculating in her head. The consumption rate of her thought capacity, remaining amount, the spread of erosion. Even as she advanced toward the village center, patching as she went, new erosion was beginning at the northern edge. Whack-a-mole. She couldn't hit them all. "If you asked whether I could stop all of it," Seto Yui said. "I'm not asking," Ratharis Ordina replied. Yui was slightly surprised. She hadn't expected this man to make the choice not to ask. She'd thought he was someone who demanded all the answers. But now he wasn't asking. He didn't slow his pace. He simply kept running beside her. His words were still sparse. But the meaning that sparseness carried felt different from when they first met. Yui silently ran toward the next erosion point. --- It was when the ruins of the abandoned syntax tower came into view. Around the half-collapsed stone tower—the ruins where syntactic experiments had once been conducted—the black light was strangely thin. There was a small space where the erosion seemed to be avoiding it. On the floor of that space, there was an opening like a vertical shaft packed with stone debris. From that shaft. A dust-covered head slowly crawled out. Teal-colored hair—or rather, hair that had lost its color under dirt and dust—caught on the edge of the shaft along with stone fragments. With small pebbles still embedded in her hair, a girl dragged herself onto the ground. Her clothes were mud-brown. In her right hand, a bundle of old parchment. In her left hand, for some reason, a single copper coin. Yui and Ratharis stopped simultaneously. The girl lifted her face. Heterochromatic eyes—left purple, right gold—looked at the two of them. When she smiled, her eyes narrowed, and a small beauty mark was visible on the left side of her nose. "Ah, I'm saved," Hanne Zorger said. The girl spoke in a carefree voice. A voice so calm it was utterly at odds with the situation. "I couldn't figure out how to get out of the underground," Hanne Zorger said. Yui stared at the girl for three seconds. "Right now," Seto Yui said. "Yeah?" Hanne Zorger replied. "The village is being consumed by erosion," Seto Yui said. "I know," Hanne Zorger said. The girl—whose name Yui would learn was Hanne Zorger—brushed the dust from the parchment and stood up. She was about one hundred sixty centimeters tall. When she unfolded the parchment, an old blueprint appeared. The lines were fine, drawn long ago. But a clear structure was visible—something cylindrical, with a sketch of inscriptions running around it. "That's why I hurried to get out," Hanne Zorger said. Ratharis fixed her with a sharp gaze. "Who are you?" Ratharis Ordina asked. "I'm the daughter of a merchant who sells antiques at the Weiss Markt in Valtis. I have a hobby of exploring ruins," Hanne Zorger said. Weiss Markt—the central market of the capital city Valtis. Why was an eighteen-year-old girl working there exploring the underground of a remote abandoned ruin? Before that question could be answered, Hanne thrust the parchment in front of Yui's face. "By the way, you're a syntax user, right? There was light flowing on the walls underground, but can you read it?" Hanne Zorger asked. "I can," Seto Yui said. "This blueprint too?" Hanne Zorger asked. Yui's eyes fell on the blueprint. The structure of a sealing device—if it was from the Sealing Annihilation War era, that would be seven hundred years ago—was drawn roughly but accurately. Just from seeing this, Yui could tell this girl was no amateur. Her hobby of exploring ruins seemed to be genuine. Ratharis spoke. "We'll confirm information underground. Guide us," Ratharis Ordina said. Hanne raised her hand happily. "Great. Um, do you know the way back?" Hanne Zorger asked. "...Is there a path underground?" Ratharis Ordina asked. "There is, but it's complicated. I got lost three times on the way here," Hanne Zorger said. Ratharis was silent for one second. Internally, Yui laughed. In this situation with the village half-consumed, this conversation was actually happening. It should have been a life-or-death scene, but somehow a leisurely tempo had emerged. It shouldn't have been funny, but it was, just a little. --- The erosion was closing in around the vertical shaft. The stone walls were being consumed by black light, crumbling from the edges. They had to descend before the entrance was sealed. Yui deployed a debug and forcibly pushed back the erosion around the shaft. A space of several meters opened up. She felt her thought capacity consumption accelerating further. "Let's go," Seto Yui said. The three descended into the shaft. The underground was vast. After descending the shaft, a stone corridor extended left and right. Syntactic inscriptions were carved across the entire wall surface. Strings of glowing text ran through the stone like circuits. Seven-hundred-year-old syntax—designed during the Sealing Annihilation War—was still functioning. Yui began reading the inscriptions on the wall. (This is—) As she read further, the full picture emerged. A syntactic research facility. A research outpost created before the Royal Syntactic Institute was established, built to maintain the seal. The location was—the outskirts of Fheren Village, underground the abandoned syntax tower. In other words. Directly beneath the abandoned cottage where she had awakened. "...No way," Seto Yui said involuntarily. Hanne leaned in from the side. "You didn't know?" Hanne Zorger asked. "When I woke up, I never thought there'd be an underground," Seto Yui said. Ratharis spoke in a low voice. "This facility and your transfer destination being the same location—unlikely to be coincidence," Ratharis Ordina said. There was no answer. She didn't know. But the question lodged in the corner of her mind. They advanced deeper into the corridor. A low growl came from around the corner. What appeared was something small. It resembled a kobold—a small underground creature—but its outline was distorted. Part of its body was frozen mid-dissolution in black light, a syntactically mutated form. A monster warped by the erosion's influence. There were three of them. Ratharis drew his sword without a word. Two strikes. It was over. The first one's flank, the second one's throat, the third one's blade had already reached it before the first fell. No wasted movement. The hand holding the sword had no emotion. Just precise and fast. "...You're fast," Seto Yui said involuntarily. Ratharis walked ahead without saying anything. Yui watched his back for just one second. Until now, she had only seen him through the cold judgment of "a tool to use." But now, for no particular reason, she saw him differently. That was all. --- In the deepest chamber underground, it was there. A stone cylindrical device roughly five meters tall. Syntactic inscriptions spiraled across its entire surface. Strings of glowing text circulated endlessly, but from the very center of the device—the deepest part—black light was seeping out. The source of the erosion. Yui approached the device and began reading the syntactic structure. It became visible. Seven hundred years ago, seven system-class syntax users had designed this seal. A mechanism to trap the overflowing energy of Nox Regalia in a circulation loop and seal it. The design itself was sophisticated. But after seven hundred years, the reference points of the circulation loop had begun to shift. The pathway meant to release excess energy had become clogged, and energy with nowhere to go was seeping outward. In Earth programming terms, a memory leak. "I thought so," Seto Yui murmured to herself. "The buffer's overflowing," Seto Yui said. Hanne leaned in from the side. "What's a buffer?" Hanne Zorger asked. "It's like when a cup has too much water and it spills over," Seto Yui said. "So if you make the cup bigger, it'll be fine?" Hanne Zorger asked. "No. You create a path for the spilled water to return," Seto Yui said. "That's complicated," Hanne Zorger said. Hanne spread out the blueprint, furrowing her brow. She pointed to another part of the parchment with her finger. "This looks like an activation switch in the blueprint," Hanne Zorger said. Yui confirmed the blueprint. The bottom of the device. A sketch of a physical activation mechanism—contact-type. Modify the device's syntactic structure, then directly touch the activation mechanism. That would restart the seal. The theory was clear. But there was a problem. The erosion being released from the source was concentrated around the device, and she didn't have enough thought capacity to approach the device while deploying debugs. She couldn't do it alone. "Your Highness Ratharis," Seto Yui said. Yui turned from the device. Ratharis stood with his arms crossed. His golden eyes watched her quietly. The sword scar on his left cheek faintly glowed in the black light leaking from the device. "Let me explain the situation," Seto Yui said. "Go ahead," Ratharis Ordina said. "While I correct the errors in the sealing syntax with debug, you need to physically push through the erosion discharge and reach the activation mechanism at the bottom of the device," Seto Yui said. "I don't have the strength to sweep away erosion with a sword," Ratharis Ordina said. "I know. That's why I'll debug in real-time while thinning out the areas where erosion is concentrated. For just a moment, a path that a person can pass through will open—in theory," Seto Yui said. Ratharis's eyebrow moved slightly. "In theory—what do you mean by that?" Ratharis Ordina asked. "We won't know until we try, but this is the only way," Seto Yui said. A few seconds of silence fell. Ratharis asked. "How much of your thought capacity do you have left right now?" Ratharis Ordina asked. Yui was slightly surprised. She hadn't expected hi