The weather sat in a strange middle ground. Not quite cold, not quite warm. It was nearing fall, the leaves losing their green hues as the chill slowly crept in. Business continued as usual for the Association, and the same held true for Squad 4. Training had resumed, routine on the surface, but their overseer never missed the small changes that built over time.
Erementaru watched as Nathaniel stepped into the room. Beneath his visor, his eyes widened slightly, a flicker of concern passing through him. No one else could see it, but the difference was obvious.
Compared to a month ago, Nathaniel's idle Uratsu output had nearly tripled.
Erementaru's mind ran the numbers instinctively. Whatever Arête had put him through, it had worked. At this rate, Nathaniel had likely already surpassed Shiro, Oliver, and Ria.
That wasn't something to ignore.
He wasn't the only one who noticed.
Ria, standing off to the side, had felt it the moment Nathaniel entered. As the daughter of Arête, she understood exactly what that kind of growth meant. As a sensory-emitter type, his presence pressed against her perception, dense and unstable, yet somehow controlled.
Her mother's influence lingered within him. Faint, but unmistakable.
She knew the method.
Force-feed power past the point of overload. Break the body's limits, then force it to adapt or collapse. It was reckless, borderline insane, even by their standards.
And yet, Nathaniel had endured it.
His energy didn't spike or flare. It sat there, heavy and coiled, volatile but restrained. Beneath it, there were inconsistencies subtle distortions in the flow, like something buried deeper than just Arête's imprint.
Something else was there.
Nathaniel, unaware or unconcerned, moved as he always did.
He tapped Shiro lightly on the shoulder.
She turned, steel-grey eyes meeting his silver ones. She gave a small nod, her expression softening into a quiet smile. His presence didn't unsettle her the way it did the others. If anything, it grounded her.
He spoke.
She answered with practiced sign language, fluid and precise.
For a moment, things felt normal.
Then Erementaru's voice cut through the room.
"Today's training is sensory-based."
The atmosphere shifted instantly.
"In a biome, sight is a luxury. When that's taken from you, hesitation gets you killed."
A pause.
"You've all heard of the Opus Incident."
No one spoke.
The memory of it lingered in the Association's records. The first recorded pitch-black, sensory-dampening biome. No light. No reliable perception. Just disorientation and death.
"You won't rely on your eyes today," Erementaru continued. "You'll rely on everything else."
His gaze lingered on Nathaniel for just a fraction longer than the rest.
"Especially you."
He pressed a button on the console.
Heavy blast doors slammed down one after another, sealing the room. The last strip of light vanished, swallowed whole.
Darkness.
Absolute.
The only thing left was the faint orange glow bleeding from Elementaru's suit and cybernetics, dim and barely outlining his frame.
Then he moved.
A sudden impact.
His fist slammed into Nathaniel's torso, sending him skidding back across the floor before anyone could react.
For a split second—
Cyan flames burst to life.
They flared from Nathaniel's body on instinct, wild and reactive, casting sharp light across the room—
Then they collapsed.
Snuffed out.
Not by force… but by lack of reference. Without sight, without orientation, the energy couldn't stabilize.
Darkness reclaimed everything.
No light. No direction.
Only heat.
Only presence.
Only instinct.
They were blind.
Erementaru's voice cut through the void.
"This room replicates the Opus Incident conditions."
A step.
Soundless.
"No light. Distorted spatial awareness. Your sense of direction will betray you."
A sharp shift—
George lost his footing, crashing into the ground.
Ria followed a second later, her balance collapsing as if the floor had tilted beneath her.
"If your equilibrium is compromised," Erementaru continued calmly, "you are already dead."
Movement surged.
Alucard struck toward where Erementaru had been—
But hit nothing.
Empty air.
A displacement. Subtle. Precise.
Erementaru was no longer there.
"You're wondering how I'm tracking you."
Another step.
Perfectly placed.
"This… is what you're here to learn."
A pause.
"Aura Shift."
"Expel Uratsu around you in a wide burst, like a pulse. If you have enough, keep it active. At first, it should work like a snapshot, then use your specific augment as a frame of reference, the traces of your power in the space you occupy."
He shifted slightly, then pointed toward Oliver.
"And you, Oliver, you can already see me clearly. It is your element in here. You are at your best now, so show me what you have."
As soon as he finished speaking, shadow-like bodies emerged from in front of, behind, and beside him. Oliver's clones rushed all at once, striking from every angle.
Erementaru smiled beneath his visor. His eyes pulsed with power as he activated his augment. In an instant, he was forty meters ahead, every clone rupturing and dissolving into darkness behind him.
He turned just in time to see Alucard trying to drive a blade into his back. He parried the strike.
A sharp scent of ozone filled the air.
Then George landed a clean blow across him.
In the darkness, George's eyes glowed faintly. He could not see clearly, but he did not need to. His power left thin outlines in the dark, and his own sensitivity to electrical signals helped him keep track of movement.
Alucard, by contrast, was working with something different. To him, the room was not clear, but it was readable. More like a slow frame-rate image, guided by blood flow and organ placement.
Shirou joined in next, wearing Erementaru down with a sonic wave. Ria followed quickly after, already familiar with the technique from training under her mother and father in her teen years. She opened fire on him while he responded with energy tendrils, forcing them back.
Nathaniel, still trapped in the dark, felt his balance shift again.
The others were keeping pace somehow.
He stayed still for a moment, thinking.
Then he stretched his senses outward.
The sensory range widened.
He felt the Ura in the false biome itself generating the effect.
So he pulsed his own Uratsu.
For a brief second, everyone in the room felt a strange tug, a subtle pull that anchored them in place.
Nathaniel's eyes finally lit with a dim cyan glow. His iris shifted subconsciously, activating his rainbow mantis shrimp sight. Suddenly, he could feel everything in the room.
A dimmed picture of the surroundings formed in his mind.
He moved.
He slipped past the others and drove a blow into Erementaru's sternum, paying him back for the earlier cheap shot.
Then he released the second, subconscious hold.
Erementaru skidded back, but he was smiling.
"Good. You all did it. But you will train to improve that sense. Think of it as your sixth sense. This technique is taught to most knights who possess emitter-type abilities."