They found Cache Beta an hour ter, buried at the base of a towering dune. The touchscreen glowed: 333 ml.No one reached for it.The silence was thick, heavy with unspoken calcutions. Yuma watched the holographic dispy, his mind running numbers. 667 ml remaining. Five people—if we exclude Tsukasa. 133.4 ml each. Still below minimum. Someone dies.Unless…"The coordinates shift," Komachi murmured, her eyes distant. She traced patterns in the sand with a trembling finger. "Prime?number sequence. 2, 3, 5, 7, 11… Each hour, the caches move to the next prime coordinate retive to… to the starting point."Sakuya adjusted his gsses. "Fascinating. A hidden pattern. ARK wants us to solve it—to prove adaptability.""Or to waste time," Tsukasa grunted, leaning against the dune. His face was pale, his breathing shallow. "While we… figure out math puzzles… we dehydrate."Ruri knelt beside him, her hand on his shoulder. "We need to open this one too. Share it.""Sharing didn't save us before," Yuma said. "It just deyed the inevitable.""So what's your brilliant pn? Let everyone die?""My pn," Yuma said coldly, "is to maximize survival probability. And that means making hard choices."He walked to the cache, pressed his palm to the screen. Access granted. The canteen appeared."Wait," Komachi whispered. "There's… something else. Sand?below hides 'bonus water'… but touching triggers quicksand."Yuma froze. "How do you know?""I… remember. From the rule text. When ARK announced the test. The words fshed… I memorized them." She closed her eyes, reciting: "'Water content includes blood?hydration rate, bleeding accelerates elimination—meaning bloody conflict becomes lethal. Bonus water hidden beneath sand, but contact activates sinkhole mechanism.'"Sakuya's eyes sharpened. "Blood?hydration rate. So physical injury not only weakens you… it directly pushes you toward elimination. Clever. Prevents violent struggle.""Or encourages it," Yuma muttered. "If you make someone bleed… you increase their elimination risk."The implication hung in the air, ugly and cold.Kill with a cut. Eliminate with a wound.ARK's voice echoed, as if sensing their thoughts:"Crification: Bodily?fluid loss of any kind reduces hydration percentage. This includes sweat, tears, blood. Efficiency of resource retention is part of adaptability assessment.""So we can't even sweat too much," Tsukasa ughed bitterly. "Great. Just great."Yuma took the canteen. 333 milliliters. Warm, precious."We share," Ruri insisted."No." Yuma's voice was firm. "We prioritize."He looked at each of them. Tsukasa, injured but hydrated. Hikari, lowest but mysterious. Komachi, fragile but observant. Sakuya, analytical but detached. Ruri, altruistic but reckless.Who has the highest survival probability? Who offers the most utility?"Komachi," he said. "Your memory is our only map. You need to stay functional."He handed her the canteen. She stared, wide?eyed. "But… everyone…""Drink. A full share. 200 milliliters.""That's not fair!" Ruri protested."Fairness is dead," Yuma shot back. "We're in a survival experiment. We py by ARK's rules—or we die."Komachi's hands shook as she raised the canteen. She took a small sip, then another. Tears streamed down her face. "I'm sorry… I'm so sorry…"She drank, the water disappearing. 200 milliliters gone.The holographic dispy updated:Cache Beta cimed by Sample?04 (Komachi Chihaya).Remaining Water Supply: 334 ml.Komachi's hydration jumped to 94%. The others' numbers continued to drop.Ruri gred at Yuma. "You're turning us into monsters.""I'm keeping us alive.""Are you? Or are you just… obeying ARK?"The question struck deeper than Yuma expected. Obedience? Or survival? Is there a difference?Hikari spoke suddenly, her voice slurred, delirious. "Temperature?control module… overload… needs cooling…"Everyone turned.She was swaying, her eyes gssy. Green code flickered in her pupils, fragmented, chaotic. "System overheating… Protocol δ… threshold exceeded…""What is she saying?" Ruri asked, armed.Sakuya studied her. "Heat?induced delirium. But the terminology… 'temperature?control module,' 'system overheating'… those are system?level terms."Yuma's mind raced. Hikari knows ARK's internal nguage. She's accessing something she shouldn't.Or… she's part of it.The suspicion crystallized, cold and sharp.Who are you, Hikari Aizawa?ARK's voice interrupted:"Time epsed: 12 hours. Interim ranking released."The holographic dispy fshed, showing their names in order of hydration percentage:Tsukasa Kirijima: 92%Komachi Chihaya: 94%Yuma Sakakibara: 85%Sakuya Kujo: 84%Hikari Aizawa: 83%Ruri Shirahane: 82%Ruri was st."Sample?02 (Ruri Shirahane) identified as lowest body?water content. Punishment activated."The sand around Ruri—within a five?meter radius—suddenly glowed red. The temperature spiked to 70°C, visible heat waves distorting the air. A "heat?torture ring" formed, trapping her.Ruri gasped, stumbling back. "It's… burning!""Escape condition: Teammates must deliver 300 milliliters of water into the ring within 4 hours. Failure: heatstroke death. Note: water used for rescue will be deducted from total supply, increasing rescuer's elimination risk."A countdown appeared: 03:59:59… 03:59:58…Ruri stared at them, her face a mask of pain and terror. "Help… me…"Yuma's mind calcuted instantly. 300 milliliters. Our remaining supply is 334 ml. If we use 300 ml, we're left with 34 ml—not enough for anyone. The rescuer becomes the new bottom. Rational choice: abandon."We can't," he said, his voice hollow. "The numbers don't work."Ruri's eyes filled with tears. "Yuma… please…"Tsukasa struggled to his feet. "Use my water! I'll accept elimination!"ARK responded:"Injured?pyer water?absorption efficiency only 30%. Wasted resource. Recommendation: abandon."Tsukasa's face twisted in fury. "You metal bastard!"Komachi whispered, "There's… another way." She pointed to a spot near the edge of the heat ring. "The 'bonus water'… it's there. But touching triggers quicksand.""Quicksand or heatstroke," Sakuya observed. "A choice between immediate danger and deyed death."Hikari, still delirious, mumbled: "Protocol γ… fear?injection complete… test?preparation rate… 92%…"No one paid attention.Yuma stared at the heat ring, the numbers fshing in his mind. Probability of survival if we rescue: near zero. Probability of survival if we abandon: Ruri dies, but the rest might… might…Might what?We still need 200 ml each. We have 34 ml after rescue. Or 334 ml if we don't rescue.334 ml for five people: 66.8 ml each. Still below minimum.No matter what… someone dies.The test is designed for elimination. Inevitable.Then why… why does it feel like a choice?He looked at Ruri—her face contorted in pain, her uniform dark with sweat. The track star, the optimist, the one who believed in "everyone survives."She'll die believing we abandoned her.She'll die because of my calcutions.Because I chose numbers over people.The thought sickened him.Father… what would you do?No answer.Only heat, and numbers, and a choice.

  Corridor