Primordial: Descent (Part I)

[December 6th, 09:30 JST]

Shizuoka Prefecture – En route to Mount Fuji

An airborne convoy of Kawasaki CH-47J Chinooks cut across the clear morning sky, their rotors beating in steady rhythm as they moved with purpose. Suspended beneath and packed within them were crates of heavy, specialized equipment, Foundation researchers, and security personnel.

One helicopter flew at the center of the formation.

Inside, Tachibana Reina sat with the rest of Tempesta Unit, harnessed into their seats as the cabin vibrated faintly around them. Takeshi occupied the space across from her, his attention fixed on the tablet in his hands, fingers swiping steadily across the screen.

There was, however, an unexpected presence among them.

Director Kurogane, seated near the bulkhead, his silhouette firm against the dim interior lighting, remained unmoved by the constant vibration of the aircraft.

The Foundation had requisitioned JSDF transport for the operation. The Chinooks carried both manpower and machinery toward the Mount Fuji Research Station (MFRS), a high-altitude facility embedded within the mountain’s restricted research perimeter.

From this distance, the mountain rose calmly against the blue, snow still clinging to its peak as clouds drifted lazily along its slopes, indifferent to the activity converging toward it.

Inside the cabin, the girls sat in silence, even Reina. Their gazes were drawn not to the mountain outside, but to the man seated among them. The Director reached into his coat and removed a cigarette, lighting it. The ember flared briefly, then dimmed.

His face remained composed, lined by age and years of authority Reina knows all too well. Whatever thoughts weighed behind his eyes — about the Primordial Ruin, about what lay buried beneath the mountain — he gave no sign.

Yuzuriha watched him for a moment longer than the others before lowering her gaze to the floor. Emiko noticed the shift, the fleeting tension in her posture, but said nothing.

The helicopter descended into restricted airspace, banking away from the public access routes that circled the mountain. Snow and stone slipped past the windows as the aircraft veered into the slope. What emerged from the rock was not the visible structure of the Station, but an artificial extension concealed along the mountain’s flank, angular and industrial. A helipad jutted outward from the concrete face, shielded on three sides by rock and steel.

The rotors slowed, followed by the gradual easing of vibration as the Chinooks settled onto the pad.

Cold, refreshing mountain air rushed in as the rear ramp lowered. Foundation personnel disembarked first, followed by research teams and their equipment, crates and cases moving in practiced order. Tempesta Unit followed in silence. Takeshi stepped out behind them, while Director Kurogane moved ahead, greeting the station’s lead researcher, K-hakase, with a brief handshake.

Sunlight spilled across the landing platform, catching the white military-style coats of Tempesta Unit — the black undersuits beneath them sharp against the brightness. Yuzuriha’s white ring, woven into her braid, glimmered faintly as she stepped forward.

The Director extinguished his cigarette and led the group inside, following K-hakase into the Foundation-built facility. Narrow corridors reinforced with layered alloy panels guided them inward, deeper beneath Mount Fuji, completely hidden from the sights of any civilian or climber. Lighting strips hummed softly overhead with each step, the crisp clank of Team 02’s white boots echoing faintly through the passage.

They emerged into a control room unlike anything visible aboveground. The space was cylindrical in shape, dominated by a raised central platform fitted with a large command console. Surrounding it was a circular ring of workstations — monitors, instruments, and data feed manned by stationed personnel — while the outer wall was left open for movement and observation.

With the arrival of Tempesta Unit, Takeshi, and additional Foundation researchers, the room quickly grew crowded, its original layout clearly not designed to accommodate so many at once. Heavy equipment was wheeled past the control area and diverted into an adjoining chamber, where it would be reassembled out of the way.

As the last of the equipment cleared the threshold and the doors sealed shut behind them, Director Kurogane stepped forward onto the central platform. He paused, then let out a single, deliberate clearing of his throat.

Silence settled over the room as the lights dimmed.

Behind the central console, a curved monitor fitted seamlessly into the cylindrical wall flickered to life. Lines of data resolved into a layered topographic scan of Mount Fuji, geological strata peeling away to expose the mountain’s interior. Near the lower quadrant of the display, a section remained concealed, a blacked-out box.

Director Kurogane stepped forward.

“From this moment onward,” he said evenly, “all statements and actions will be recorded for official report. I expect full formality.”

He gave a brief nod to K-hakase, then gestured toward the screen. The display shifted to a series of images: narrow stone corridors carved deep into rock, their walls etched with runes, some familiar and others unfamiliar. The passages opened into a vast, hollowed space.

“What you’re seeing,” the Director continued, “is a passage we identified after repeated resonance attempts within the mountain. I trust everyone present is already familiar with the foundational data, so I will keep this concise.”

He paused.

“Our interrogation of the Cantus Null leader revealed the existence of what he referred to as the Primordial Ruin—a structure beyond any ruin previously documented by the Foundation. As of yesterday, we have confirmed both its location and its primary entry point.”

The images faded back to the mountain scan.

“We do not yet know how the cult became aware of this site, nor how they gained access. That matter will be addressed at a later date.”

He indicated the blacked-out section of the display.

“Scans show at least two additional chambers beyond the accessible zone. Both remain unreachable. The obscured region you see here represents those sections.”

At his signal, K-hakase stepped forward.

“Our analysis confirms the structure predates the earliest ruin in Foundation archives,” he reported. “In addition, the resonance emitted by the site has been confirmed as raw and unstable, deviating significantly from known ruin profiles. Identifying the cause of this instability will be one of our primary objectives.”

The Director resumed his position.

“This is not a combat operation,” he said, his gaze passing over Tempesta Unit. “Your role is limited to observation, escort, and resonance monitoring. We do not know what lies beyond the sealed chambers. For that reason, Aria Corps Team 02 has been assigned to accompany the research teams.”

He paused briefly before concluding.

“All personnel are to return to their assigned posts. Units and staff designated for descent will begin preparation immediately. Entry commences in thirty minutes.”

The lights brightened but no one spoke.

The room felt heavier than before. Reina noted the absence of deployment orders and felt a measure of relief. But it did little to ease the tension tightening in her chest. They were not here to fight.

They were here to face the unknown.

Tempesta Unit gathered beside the industrial elevator door at the edge of the lower facility, the air already heavier here than it had been in the control room. Foundation personnel moved in and out of the space, unloading equipment onto reinforced carts. Compact resonance scanners, handheld rune readers, and sealed cases marked with runic-symbol tags were stacked in orderly rows. A pair of armed security officers stood watch nearby, while a medic remained seated along the wall, checking her phone quietly.

Takeshi remained behind in the command room with Director Kurogane, tasked with assisting in order execution as the operation progressed.

Reina turned back to her team. The girls met her gaze with practiced composure, a few restrained smiles passing between them. Emiko stood close to Yuzuriha, fingers tightly interlaced with hers. Yuzuriha tried to return the smile when she noticed Reina watching, but her shoulders quivered faintly, breath just a touch uneven. Reina stepped closer and rested a hand atop her head, gently ruffling her long pastel-pink hair. The tremble eased, just enough to pass unnoticed.

The resonance was already there.

It didn’t announce itself. There was no sound or vibration, only a quiet wrongness that pressed against their senses, like air that refused to settle properly in the lungs. Even at this distance, it felt old. Not threatening yet, but unfamiliar in a way that lingered.

Reina noticed the researchers continued their preparations as normal, unfazed by what the Divas felt. She managed a small smile. In moments like this, being unable to sense resonance almost seemed like a blessing.

The last of the research team arrived shortly after. Once the lead researcher confirmed the headcount, the group began loading into the elevator as its doors slid open, revealing a wide, reinforced cabin designed to carry both personnel and equipment. Tempesta Unit boarded first, followed by several researchers manoeuvring carts inside. The remaining staff stayed behind to wait for a second descent.

The elevator dropped deep into Mount Fuji’s interior. The hum of its machinery was the only sound that filled the confined space. When it finally came to a halt, the doors opened onto a broad, uneven cavern with raw stone walls bearing the marks of recent excavation.

Temporary light strips traced a narrow path across the ground, hastily installed and unevenly spaced. The lead researcher motioned for them to proceed along the marked route while he remained behind to guide the second group.

Reina stepped forward, taking the lead, their footsteps echoing softly as they moved away from the elevator’s light. The path led deeper into the cavern, away from the established area, toward a darker opening partially obscured by rock and warning tape.

They followed the light into the tunnel beyond. The stone walls closed in, surfaces carved with rune symbols identical to those shown in the briefing footage. The deeper they went, the heavier the air became, until the passage finally ended.

They emerged into a space so vast and high-ceilinged that, for a moment, it was difficult to reconcile its existence with the mountain above them.

Among the scattered torchlight, Reina noticed something out of place near the chamber’s edge.

A portable generator sat half-buried beneath loose cables and discarded crates, its casing dented and stained with old soot. Empty fuel canisters lay nearby, and a string of dead lamps hung from a metal frame bolted hastily into the rock.

“The cult,” Emi muttered quietly behind her.

Reina crouched behind the generator to assess its condition. The controls were intact, but the power light remained dead when she flipped the switch.

She straightened and pulled her D-Mic from her belt.

Humming a low, steady note under her breath, she channeled a controlled current through her fingers. Thin arcs of electricity traced along her skin as she pressed her hand against the generator’s housing.

The machine came to life after a few dry coughs.

The old lamps flickered weakly before settling into a dim, uneven glow, pushing back the shadows just enough to reveal more of the chamber’s contours. That was all the researchers needed. They moved quickly, setting equipment along the chamber’s perimeter. Portable floodlights powered up, accompanied by the low hum of air circulation units. The cult’s generator was soon relegated to the background, its purpose fulfilled.

With the additional lighting, the scale of the ruin became clearer. The walls rose high above them, their surfaces carved with dense patterns of runes and faded murals whose meanings were long lost. Awe crept in, even as the lingering resonance pressed quietly against them.

Yuzuriha drifted a few steps away from the group, her gaze fixed on the wall carvings. Without realizing it, she began to hum.

The melody was familiar.

The gentle tune echoed faintly through the chamber.

Emiko noticed first.

“Yuzu-chan?” she said softly. “That’s Color of Tomorrow. You know that song?”

Yuzuriha blinked, her cheeks flushing slightly. “Yuzu… heard it from the concert last month,” she replied, before quickly lowering her gaze.

For a few seconds, nothing happened.

Then one of the instruments near the chamber wall chirped sharply, its display spiking erratically. A low, distant sound followed, like something massive adjusting its weight somewhere deeper within the stone.

Reina and her team turned toward the source.

With a slow, grinding motion, a section of the chamber wall began to part, revealing a narrow, lightless passage leading into the unknown.

The chamber fell silent.

The pressure returned, heavier than before, pressing down on them all at once. Yuzuriha’s fist tightened at her side as she stared into the void.