Morning arrived underground without sunlight. Arata knew it only because the industrial clock above the barracks door had ticked past seven.
There was no sunrise in the labyrinth, no pale line of gold stretching beneath a horizon, no birds calling from a waking canopy. There was only the steady, bone-deep vibration of diesel generators, the distant rush of subterranean water, and the occasional metallic groan of machinery buried somewhere inside the research station.
Arata finished tightening the straps of his field harness and looked at himself in the scratched metal mirror. He looked different. Not stronger—not yet—but undeniably more equipped. The dark, ancient sword rested securely against his back, its leather-wrapped grip sitting just above his shoulder, perfectly positioned for his hand. The red crystals embedded along the fuller were dormant now, but he knew what they could become.
Across the room, Ren was struggling with his own harness. More accurately, the harness was struggling with Ren.
"Hold this," Ren grunted, trying to balance the enormous ancient hammer across his lap.
"No," Arata said without looking away from the mirror.
"Why?"
"Because last time you asked me to hold it, you nearly dropped it on my foot."
"I caught it," Ren argued.
"You caught it after it hit the floor."
"Still counts."
Arata shook his head as Ren finally managed to secure the heavy strap around his shoulder. He stood, and the hammer's massive weight immediately pulled the canvas harness downward. Ren grimaced, adjusting his posture. "Forty-two pounds."
Arata looked at him. "You still remember the exact weight?"
"I remember everything that tries to kill my spine."
"Your hammer isn't trying to kill you, Ren."
Ren cast a dark glance over his shoulder at the blackened iron head. "Give it time."
A quiet voice drifted from the doorway. "You're both going to be late."
Sera stood in the threshold. Her dark hair was tied back neatly, her field uniform secured flawlessly beneath a light protective vest. The silver armlet rested comfortably around her wrist, its sapphire crystals entirely dark. They looked completely ordinary. Mochi sat perched on her shoulder, watching the two boys with an expression that somehow managed to look deeply judgmental, despite belonging to a small white creature with enormous ears.
Ren pointed an accusing finger at the animal. "Even Mochi thinks you're slow."
Mochi chittered in response.
Sera looked at Ren with flat, calm eyes. "He was looking at you."
"That is absolutely not what happened."
Arata smiled. For a few fleeting seconds, none of them thought about the dungeon beneath their feet. But then Sera's gaze shifted toward the dark hilt rising over Arata's shoulder. "Everything ready?"
Arata nodded, the humor fading into focus. "Ready."
Ren hefted the hammer, rolling his shoulders. "Ready."
Sera touched the cool silver of her armlet. "Ready."
They stepped out into the corridor. The staging area outside the Level Four access sector was already buzzing with tense, controlled activity. Crates had been moved aside to clear the deck. Climbing equipment lay meticulously arranged beside the descent shaft. Medical packs, ammunition cases, emergency oxygen cylinders, ropes, halogen lamps, and field instruments had been checked, counted, and rechecked.
Daichi stood beside the shaft, inspecting a heavy locking carabiner, while Mina quietly organized a stack of trauma supplies. Dr. Hayama stood several meters away, studying a glowing field tablet. When he saw the three teenagers approaching, he lowered the screen.
"Before we go," Hayama said, his voice cutting through the ambient noise of the staging area. Arata stopped, sensing the sudden weight in the older man's tone. Hayama looked at them for several long seconds. "Yesterday's expedition recovered more than weapons."
Sera's expression grew serious. "The remains."
Hayama nodded slowly. "The people who died down there. We've identified enough equipment to establish that many of them were adventurers. They came here long before us. They explored these exact same ruins. They searched for the exact same answers."
Arata's hand slowly settled over the grip of his sword. His mind flashed back to the massive, silent chamber. The crushed bones. The rusted, useless weapons. The collapsed packs covered in centuries of gray dust. Real people had stood where he now stood. They had fought where he had fought. And they had never gone home.
"What happened to them?" Arata asked quietly.
Hayama looked toward the dark, open throat of the shaft. "We don't know." The honesty in his answer somehow made the reality much heavier. "We don't even know how many expeditions reached that depth. We don't know how many disappeared in the dark before anyone could record their names."
Sera lowered her gaze to the floor. Arata stared into the abyss. They had entered the labyrinth because they wanted answers, but there had always been someone before them. Someone who had carried a weapon, someone who had been terrified, and someone who had decided to step forward anyway.
"Then we should remember them," Arata said, his voice steady.
Hayama looked at him, the harsh lines of his face softening just a fraction. "We will. And everything you've recovered will be preserved. The weapons. The records. The photographs. The samples. Every piece of information you bring back will be documented properly." He paused, adjusting his glasses. "And you will be compensated for the work."
Ren's head snapped up, his eyes widening. "Compensated?"
Hayama gave his son a deeply tired look. "Yes."
Ren immediately looked thrilled. Then Hayama added smoothly, "Except you."
Ren's face fell. "What?"
"You receive a monthly allowance."
"That's pocket money!"
"Correct."
"That's not compensation."
"It's compensation for being my son," Hayama countered flawlessly.
Ren stared at him in utter disbelief. "That makes absolutely no sense."
"It makes perfect sense."
"Everyone else gets paid for surviving a literal death dungeon, but I get pocket money?"
"You already get money every month, Ren."
"It is not enough money!"
Hayama raised a singular, unimpressed eyebrow. Ren folded his massive arms across his chest. "This is blatant discrimination."
Daichi looked away toward the shaft, very clearly hiding a grin. Mina pressed a hand over her mouth to muffle a laugh. Even Sera's disciplined expression cracked into a soft, genuine smile.
Hayama sighed, rubbing his temples. "Finish today's expedition, and we will discuss it."
Ren pointed a gloved finger at him. "That's a promise."
"It's not."
"It sounded exactly like one."
"It wasn't."
Ren looked at Arata. "Did you hear that?"
"Unfortunately," Arata murmured.
"I'll hold him to it."
Hayama turned away, waving a dismissive hand. "Gear up."
Ren grinned. "Yes, sir."
The tension had broken, but Arata could still feel the lingering weight of Hayama's earlier words. There had been people before them, and there would be people after them. Whatever they discovered beneath the mountain would outlive them all. That thought stayed anchored in Arata's mind as the team moved out from the station and into the subterranean forest.
They began with a warm-up. The underground timberland of Level Three was damp, humid, and thrumming with life. Bioluminescent moss coated the massive rocks, and thick, petrified roots descended from the cavern ceiling like pillars. Water ran through shallow, mineral-rich channels between the towering trunks. Compared with the freezing, sterile desolation of Level Four, it almost felt peaceful.
Almost.
Daichi suddenly raised his hand. Everyone froze in their tracks. A sharp rustling sound echoed from a patch of dense, oversized ferns. Ren shifted his stance, adjusting the balance of his hammer. Arata drew his dark sword with a smooth metallic ring. Sera raised her left arm, bracing her wrist.
A gray, multi-jointed creature burst from the undergrowth, its jaws snapping.
Arata moved first, his footwork precise. The dark sword cut a clean arc through the creature's shoulder, throwing its momentum off-center. Ren stepped effortlessly into the opening, bringing the iron hammer down in a crushing blow. The creature collapsed into the loam and immediately began to dissolve into ash.
Thin, luminescent threads of residual mana rose from the corpse. Sera's armlet responded instantly. A brilliant blue light spread across the sapphire crystals, drinking in the drifting energy.
"Charging," Sera announced, watching the mana funnel into the silver band.
Daichi checked his telemetry scanner. "Confirmed."
Another creature dropped from the canopy. Then a third lunged from the brush. The warm-up seamlessly shifted into a controlled, methodical hunt. They did not fight recklessly; they practiced. Arata learned to conserve his movement, relying on the sword's strange, flawless balance. Ren learned to pivot and control the inertia of his enormous weapon rather than letting its forty pounds dictate his footing. Sera learned to draw the ambient mana into her armlet efficiently, storing it without wasting a drop.
One creature fell. Then another. Then a third. Each death released a small, shimmering cloud of residual mana, and the ancient weapons drank it eagerly.
The red crystals in Arata's sword gradually brightened, pulsing with a deep, internal heat. The violet crystals embedded inside Ren's hammer began to hum, vibrating against the iron. The sapphire stones surrounding Sera's wrist filled to the brim with radiant blue light.
By the time they reached the deeper, unmapped sections of the forest, all three weapons were visibly, dangerously charged. Arata held his sword at the ready, a thin, crawling aura of red energy tracing the edge of the blade. Violet energy coiled around Ren's blackened iron hammer in twisting, crackling arcs of static. Blue light surrounded Sera's silver armlet like a dense, rippling halo.
Mina stared at the display of raw power. "Well."
Daichi looked at the glowing weapons, his scanner ticking rapidly. "That is considerably more output than yesterday."
Ren smiled, resting the crackling hammer on his shoulder. "Now we're ready."
Daichi immediately pointed a stern finger at him. "Don't get confident."
"I'm not confident."
"You look confident."
"I am appropriately prepared."
"You look like you're about to try and hit a mountain."
Ren looked fondly at his glowing hammer. "That is because I might."
Arata sighed, shaking his head. "Just ignore him."
Sera nodded in complete agreement. "I already do."
"Everyone is against me today," Ren complained, though he didn't stop smiling.
They pressed deeper into the cavern. The dense trees began to thin out, opening into a wide, rocky clearing.