The scent of Rivieria still clung to him, a phantom reminder of the tangled alliance he had forged. It was a complication, but also a catalyst. The ruined elf village, the memory of the knights' greed, the sheer scale of the tyranny he faced—it all screamed one truth: he was not yet strong enough. The power of Kiva and OOO was formidable, but the King's court, and whatever lay beyond, would demand more. He needed to evolve, and he needed to do it quickly.
The next morning, he found Rivieria overseeing the beginnings of the village's reconstruction. Her demeanor towards him had shifted; the formal gratitude was now layered with a quiet, intimate familiarity.
"I need to get stronger," Seiji stated, his voice low and direct, cutting through the morning calm. "Are there any areas nearby teeming with monsters? A place to test my limits."
Rivieria studied him, her forest-green eyes seeing both the man and the warrior. She nodded slowly. "To the north, a half-day's journey, lies the Maw of Ghorm. It is an unconquered dungeon, feared by our people and the humans alike. The creatures within are savage, and its depths are unknown. Many have entered. Few have returned."
A grim smile touched Seiji's lips. "Perfect."
He went alone. The Vanguard armor materialized around him as he left the village, its black and crimson form a stark contrast to the vibrant life of the forest. By midday, he found it: a gaping maw of rock, a cave entrance that seemed to breathe out an air of damp decay and ancient malice. As Rivieria had warned, it was patrolled. Goblins, scabrous and chittering, shuffled around the entrance with crude spears.
Seiji observed from the shadows, his mind cold and analytical. Low-level mobs. Disorganized. No threat. He didn't need a Rider's power for this. He was a blur of motion, a silent reaper. His armored fists and feet moved with brutal efficiency, dispatching the sentries with precise, shattering blows before they could even raise an alarm. He stepped over their still-twitching forms and into the darkness of the dungeon.
The first few floors were a grim procession. Horned wolves with glowing red eyes lunged from the shadows, only to be met with a punch that shattered bone. Mimic chests, their toothy maws snapping open, were splintered into kindling. Skeleton soldiers, rising from the dirt with rusty swords, were swept aside like dry leaves in a hurricane. None could withstand a single, focused blow. This wasn't a battle; it was a calibration. He was testing the armor's baseline capabilities, and they were immense.
He descended, floor after floor, a one-man avalanche of destruction. The dank air grew hotter, the stone walls glistening with a faint, sulphurous moisture. Finally, on the fifth floor, he reached a dead end dominated by a massive, rune-etched stone gate. He pushed it open, the grinding of stone echoing in the cavernous space beyond.
The chamber was vast, lit by a hellish glow from a pool of magma. And in the center, coiled and waiting, was the source of the heat: a Wyvern. It was smaller than a true dragon, but no less deadly, its scales the color of cooled lava, its eyes burning with primal intelligence. It fixed its gaze on him, a low, rumbling growl vibrating through the very floor.
Without a word, Vanguard charged.
The Wyvern reacted instantly, its massive head snapping forward as it unleashed a torrent of fire. Seiji dove to the side, the heat blistering the air where he had stood. He closed the distance, aiming a powerful kick at its leg joint, but the creature was surprisingly agile. With a beat of its leathery wings, it launched itself into the air, hovering just out of reach.
The battle became a deadly dance. The Wyvern strafed the chamber with fire, forcing Seiji into constant, evasive motion. He would leap onto stalagmites, using them as springboards to launch attacks, his fists connecting with the creature's underbelly with dull, resonant thuds. It was a stalemate, a test of endurance.
Then, the Wyvern changed tactics. It landed, dug its claws into the stone, and let out a deafening, ultrasonic roar. The sound was a physical force, a concussive wave that hit Seiji like a physical blow. His senses overloaded, his vision swam, and for a critical second, he was completely stunned.
The Wyvern seized its chance. It inhaled deeply, its chest glowing, and unleashed a point-blank firestorm.
The blast caught Seiji full-on, lifting him off his feet and slamming him into the far wall with bone-jarring force. He crashed to the ground, smoke rising from his scorched armor. Dazed, he tried to push himself up, his systems flickering.
It was too slow. The Wyvern was upon him in an instant, one heavy, clawed foot pinning him to the ground with crushing force. The creature lowered its head, its hot, foul breath washing over his helmet. It opened its maw wide, rows of serrated teeth glinting, ready to crush him, to swallow him whole.
In that moment, trapped beneath a monster of myth, feeling the intense heat of its draconic flame and the primal power of its lineage, the Vanguard system found its next key.
[Contact with lesser dragon-kin and sustained dragon-fire energy. Catalyst: Primal Adversity. Conditions met.]
[Unlocking: Kamen Rider Agito.]
A new kind of power flooded his system. Not the predatory darkness of Kiva, nor the combinatorial desire of OOO, but something purer, more fundamental: the power of endless evolution. The power to overcome any obstacle, to evolve in the face of adversity itself. On his internal HUD, the name Kamen Rider Agito blazed to life in a brilliant, holy-looking yellow-white light.
The Wyvern's jaws began to close.
"ACCESS FORM: AGITO TRINITY."
A shockwave of pure, golden energy erupted from Seiji's body, throwing the Wyvern back. It staggered, screeching in confusion. Seiji rose, his aura already transforming. The black and crimson bled away, replaced by a sleek, silver-and-gold halo, and the crimson dragon emblem was replaced by the angular, majestic symbol of Agito.
He stood, not as a creature of darkness, but as a warrior of light born in the heart of a dungeon. The Agito aura, a visible corona of power, shimmered around him.
The Wyvern, recovering, breathed fire once more. But Seiji didn't dodge. He crossed his arms, the Storm Halberd and Flame Saber energy manifesting as phantom weapons on his ms. With a grunt of effort, he swung two weapons forward, unleashing a combined stream of howling wind and searing flame. The interference energy met the fire breath head-on, overpowered it, and slammed into the Wyvern, pinning it against the wall in a vortex of destructive power.
Before the creature could break free, Seiji took his stance. He leapt into the air, a brilliance trail following his path. He spun, energy focusing on his foot.
[Executing Agito Finisher: Shining Screw.]
The kick was a lance of pure, evolutionary force. It pierced through the Wyvern's chest, the shining energy erupting from its back in a shower of light and scales. The monster let out one final, choked gurgle before its body went limp, slumping to the floor, motionless.
Seiji landed gracefully, the Trinity aura dissolving back to the base Vanguard aura. He looked at the fallen beast, the source of his near-defeat and his sudden evolution.
"Thank you," he said to the corpse, his voice flat and sincere. "For helping me unlock a new power."
He turned, his gaze fixed on the dark, descending passageway that promised even greater challenges. Without a moment's hesitation, he stepped over the Wyvern and continued his journey deeper into the dungeon. The crucible was not yet done with him.