The warning I saw in the control room last night was still spinning in my head. ——Mana reactor output decline detected. Estimated operational days remaining at current output: 7 days. Seven days. The number kept circling through my mind even during dinner. Emiya's food was delicious, but I could barely taste half of it. Fujimaru Ritsuka got out of bed. Black short hair stuck up messily from sleep. The mole on their left cheek caught the morning light. Today, I had to tell everyone. The mana reactor—a massive energy device that supported Chaldea, the Humanity Continuity Guarantee Organization. A complex system of a nuclear fusion reactor and mana conversion apparatus deep underground, supplying power to the entire facility. If that stopped, Chaldeas stopped. If Chaldeas stopped, the system maintaining the Servants' manifestation stopped too. In other words, everyone disappeared. Ritsuka was the Master supplying mana to the Servants, maintaining their manifestation. Three Command Spells—marks of contract with Servants—were carved into the back of their hand. All the heroic spirits gathered here existed only because Ritsuka was here. The device protecting their lives might stop in seven days. I put on a white shirt and stepped into the corridor. The Main Corridor—a 200-meter main passage running east-west through the facility. At this hour in the morning, it should have been bustling with staff moving about, Servants heading to the training grounds or the cafeteria. Should have been. I took three steps and stopped. The corridor was gold. Urns. Swords. Crowns studded with jewels. Golden horse figurines. A necklace in a transparent glass case. A shield with a massive ruby embedded in it. They lined the corridor from end to end, orderly, without gaps. The blue floor lights reflected off them, glittering like I'd wandered into a jewelry store warehouse. Three staff members stood stranded at the corridor's entrance. Beyond the treasure, at the far end of the corridor, a man stood. He wore golden armor. Hands on his hips, standing with legs apart. Long golden hair tied back, sharp and gleaming golden eyes surveying the line of treasures with satisfaction. Tall. At least 185 centimeters. A short sword hung casually in one hand. His attitude was absolutely massive. "[angry]We can't get through!" "[cold]I'm appreciating them. Be silent." The staff member held their head in their hands. Ritsuka approached slowly, glancing sideways at the treasure line. I'd seen this man from a distance yesterday. There was a golden shadow at the far end of the corridor—was that him? Gilbert Zahal. One of the Servants, supposedly an ancient hero-king. I'd heard he possessed a treasury as his Noble Phantasm. ……It made sense. "[gentle]Um… excuse me." Gilbert glanced over. Golden eyes swept from top to bottom, examining Ritsuka. "[serious]So you are the one. The Master, I presume." "[gentle]Yes. Could you maybe clean this up a bit…?" "[cold]Clean it up, you say?" Gilbert's brow furrowed. Then he swept his arm out, gesturing to the line of treasures. "[excited]I selected this location for my exhibition of supreme treasures—the place with the finest natural light. The morning sun illuminates this spot most beautifully. How fortunate. You surely have time to spare. Let me begin with this teapot in front." Ritsuka didn't even have time to say "what?" Gilbert's hand lifted a pure gold teapot effortlessly. "[serious]This was crafted upstream of the great river, before my era. It boasts a purity impossible by the metallurgy of that time. See this pattern on the surface—look carefully, here—the craftsman carved it in millimeter increments. The records say it took three years to make. It was used at banquets, but wouldn't you hesitate to actually pour tea into something so exquisite?" "[gentle]Y-yes…" "[serious]Next. Look at this ruby. The mountain it came from erupted and vanished 100 years ago. Which means this is the last one in existence." "[surprised]The last one…?" "[excited]Precisely. No one but I possesses it. That is why it has value. Now, regarding this sword—" Ritsuka began to panic internally. (I have to cut this short… One of my seven days is…!) But Gilbert's eyes were genuinely delighted, and when he looked at his treasures, a soft light shone in those golden eyes, different from their usual sharpness. Ritsuka couldn't bring themselves to dismiss him outright. "Gilbert, just for a moment—" "[cold]Wait. I'm at the best part." He'd already moved to the next treasure. Ritsuka gave up and walked alongside him, offering responses while they moved through the treasure line. Gilbert wouldn't stop talking about each piece. The ivory figurine came with stories of its origin, creation date, and the politics of that era. The silk tapestry had tales spanning three generations of weaving families. The glass lantern carried an anecdote involving a certain princess. An hour had passed before I realized it. When they reached the corridor's end and Gilbert lifted the final treasure—a small stone gleaming in seven colors—Ritsuka finally spoke. This time, they interrupted. "[serious]Gilbert. There's something really important I need to tell you." Gilbert's hands stopped. He must have noticed the change in tone. Golden eyes turned to Ritsuka. "[serious]The mana reactor might stop in seven days." Silence. Gilbert's expression changed for the first time. Not the delighted face from explaining the stones. A serious one. "[serious]…The mana reactor is…" "[serious]Chaldea's power source. If it stops, all systems shut down. Chaldeas stops, and we can't maintain the Servants' manifestation." Gilbert was quiet for a moment. Then he crossed his arms. "[serious]My treasury surely contains a tool or two. Fear not, Master." Ritsuka felt a spark of hope. The treasury—Gate of Babylon, as Gilbert's Noble Phantasm was called. A Noble Phantasm was a crystallization of weapons, abilities, or legends a Servant possessed in life, transformed into supernatural armaments. Using them was powerful but costly. Gilbert's treasury supposedly contained literally anything—maybe repair tools too. Gilbert opened his treasury. The first thing that came out was a pure gold teapot. The one he'd spent an hour explaining earlier. "[cold]…Not this one." Next came a chess set studded with jewels. Then an ivory carving. A silk tapestry (a different one). A golden candelabra. A silver dinnerware set. A crystal vase. Seventeen jeweled necklaces. A mountain of gold coins. No tools. "[serious]Not this either. Then perhaps…" He was getting stubborn. Every time Gilbert opened his treasury, more treasures poured out. The corridor, already buried in wealth, accumulated more and more. It became a mountain of treasure. A staff member screamed. "[angry]We can't get through! The corridor is completely blocked!!" "[scared]We can't reach the medical section!!" "[serious]Gilbert, stop for a moment!" "[cold]Just a bit longer. I'm certain it's here." It didn't stop. A jeweled chess set (second one). An ivory figurine (different one). A gold teapot (yet another). Everything gleamed and glinted, bouncing the blue light from the floor lamps, until it was impossible to tell if this was a corridor or a treasure mountain. The sound of all the staff members taking detours echoed in the distance. Gilbert finally stopped. A long silence. "[whispers]…Perhaps my collection philosophy has a flaw." It was barely a whisper. Really barely. Ritsuka almost laughed but held it back. "[gentle]…You didn't put practical items in there, did you?" "[cold]I have collected beautiful things. Tools have no beauty." "[gentle]Well… I suppose that's true." The two of them silently began cleaning up the treasures. Gilbert returned them to his treasury. Ritsuka picked up rubies rolling across the floor and handed them over. While cleaning, Ritsuka pulled up a terminal from the control room and accessed it. Trismegistus, the spiritual calculation device—Chaldea's ultra-high-performance computer with access to all facility data—and opened the logs. The reactor core materials section. "[surprised]…Spiritual vein stone." "What?" "[serious]The name of the ore used in the mana reactor's core. Spiritual vein stone, apparently. And… Chaldea's stockpile is zero." Gilbert stopped moving. Ritsuka continued. "[sad]We can't get supplies from outside either. Chaldea is in the Himalayas, 6,000 meters above sea level. There's no supply route. We have to solve this with what's here." Gilbert was quiet for a while, returning a golden candelabra to his treasury. "[serious]…Spiritual vein stone." Then, quietly: "[serious]In my era, there was a similar stone. It was mined from ore veins infused with mana, said to be crystallized earth power." Ritsuka looked up. "[serious]Chaldea is built into the mountainside of the Himalayas. If the mountain's spiritual veins are close…" He trailed off, stopping his cleanup work. Ritsuka and Gilbert looked at each other. "[excited]The library." "[serious]Let's go." They hurried through the rest of the cleanup and headed to the library together. The library was on the third floor, west wing. A six-meter-high vaulted ceiling structure with bookshelves covering the walls. 120,000 volumes in the collection. Everything from grimoires to history books to documents from every era, mixed with books the Servants had brought. Gilbert stood before a shelf, arms crossed, looking up at the ceiling. "[serious]Where are the construction records for Chaldea?" "[gentle]You can tell?" "[cold]I am a collector. I know where documents are kept." It was mysterious confidence. But he walked straight to a shelf without hesitation, ran his golden finger along the spines, and pulled out a single book. "[serious]Chaldea Facility Construction Records. Should include the geological survey report from completion." The two sat on the floor and turned pages. Gilbert's golden fingers turned them. Ritsuka leaned in from the side. Dusty pages continued. Survey data. Ground firmness. Water vein locations. Geothermal readings. Ritsuka spoke up. "[excited]This is it!" A passage from the geological survey report. ——Signs of ore deposits infused with spiritual veins detected near underground level 3. No obstruction to construction. "[excited]Underground… there might be spiritual vein stone!" Gilbert crossed his arms and snorted. "[serious]As I said." Ritsuka turned the page. Tried to read the next line—and stopped. Gilbert saw it at the same moment. ——The aforementioned underground passage was sealed due to deterioration after construction completion. Currently off-limits. Signs of collapse in portions of the passage. Silence. Ritsuka stared at the page, dazed. (We came this far…) Hope appeared, and immediately a new wall rose. A deteriorating passage on the verge of collapse. Off-limits. Deep underground in Chaldea, spiritual vein stone might exist. But the path to it was crumbling from age. Gilbert lifted his eyes from the page. He looked toward the window—the library had a small skylight letting in white light—and spoke quietly, arms still crossed. "[serious]…Obstacles are inevitable." Ritsuka looked at his profile. The show-off who wouldn't stop bragging about treasures, who'd turned the corridor into a sea of wealth, now wore a completely different face. Quiet, composed, and somehow—reliable. Ritsuka read the report's text again. Signs of collapse, it said. Signs. Not collapsed. "[serious]…Can we make it?" "[serious]We won't know unless we try." A short answer. But it was enough. Quiet light filtered into the library. Outside was the slope of a Himalayan mountain, and beyond the thick walls lay minus-30-degree cold. But here, now, it was warm. Seven days. Now six remained. The underground passage was crumbling from age, and whether spiritual vein stone even existed was still unknown. But t