Fate's Slave - Shadow Slave X Honkai Star Rail

Sunny’s shadow rippled.

Something massive moved within it, displacing darkness like a tide being forced backward. The shadows beneath his feet thickened, stretching outward and upward as if answering a silent summons that carried far more weight than before.

Then Saint stepped out.

She emerged from Sunny’s shadow as if breaking free from a cocoon of night, onyx armor unfolding into the world with a low, resonant pressure that made the air itself recoil. The Ascended Demon was no longer merely taller than Sunny.

She dwarfed him.

Her height tripled in an instant, her massive frame rising to tower over both Sunny and Kafka alike. Each step she took caused the fractured rooftop to groan, reinforced plating buckling under her weight as cracks spiderwebbed outward. A billowing cape of condensed darkness unfurled behind her, flowing unnaturally despite the lack of wind, as though reality itself was being pulled along in her wake.

The crimson glow behind her visor intensified.

What had once been two glowing orbs became an overwhelming flood of red light, consuming the entirety of her visor until it seemed as though an inferno burned behind the onyx steel. Her gauntlets elongated, edges sharpening into brutal, angular weapons designed solely for destruction. Her shield expanded as well, growing into a slab of shadow-forged mass large enough to serve as a moving bulwark.

As Saint turned, something else formed.

A black greatsword manifested in Sunny’s hands, forged instantly from dense shadows. It was colossal, its blade alone longer than two grown adults laid end to end, its surface swallowing all light that dared touch it.

Sunny did not hesitate.

He tossed the greatsword upward with casual precision.

Saint caught it effortlessly, fingers closing around the hilt as though its impossible weight meant nothing. The rooftop dipped beneath her stance as she brought the blade down to rest against her shoulder.

For a moment, she stared at Kafka.

Then she turned back toward Sunny, tilting her head slightly.

The gesture was almost... questioning.

Sunny scowled.

"What are you waiting for?"

Saint glanced between Sunny and Kafka once more. Then she shrugged.

And moved.

The instant Sunny sent his three shadows surging away from himself and into Saint’s form, the world seemed to lurch. Gloomy, Haughty, and Happy layered themselves onto the Ascended Demon, their silhouettes melting into her armor, reinforcing her existence rather than Sunny’s.

The price was immediate.

Sunny felt the loss at once, his own presence thinning as the augmentation left him. His strength dropped sharply, shadows around him growing less dense, less absolute.

Saint, however... she became monstrous.

Her already immense presence surged again as the triple augmentation took hold, Shadow Essence roaring through her enlarged frame. The greatsword came down in a sweeping arc that carved through air and space alike, pressure alone shredding debris into dust.

Kafka met her charge head-on.

***

Kafka felt it immediately.

Irritation.

It was faint, subtle, but unmistakable.

’So unfair...’

That was the word that surfaced unbidden in her mind as Saint rushed her down, each step cracking the rooftop beneath her feet. Kafka sidestepped the first strike with casual grace, Saint’s blade crashing down where she had been a moment prior and cleaving straight through the structure, sending chunks of reinforced alloy spiraling into the void below.

Some people had normal movesets.

Kafka considered herself one of them. Aspects could be versatile, sure, but they weren’t all-encompassing.

The other two Divine Aspect holders she knew were either a one-trick, or a three-trick pony. They were very good at performing those tricks, though.

Sunny, on the other hand, had the infuriating habit of turning nearly any idea into a viable option. It was obvious he has never tried this before.

Saint’s sword came again, faster this time.

Kafka deflected it cleanly, magenta steel sliding along the black blade with a screech of compressed force. Despite Saint’s mastery — because yes, the Ascended Demon was an absolute master of the blade — the gap in Rank still existed.

It had been narrowed.

But not erased.

Kafka danced backward, boots barely touching the ground as Saint followed relentlessly, shield raised, sword swinging in brutal, technically flawless arcs. Each strike was calculated, layered with power and precision that would have obliterated nearly any Ascended being.

Kafka parried.

Deflected.

Redirected.

She moved like a spider slipping through a closing fist.

From the corner of her eye, she felt it.

Movement in the shadows.

He leaped from darkness behind her, Hail Sorrow raised for a killing blow. Kafka shifted her weight by a fraction, Saint’s sword crashing past her shoulder as Kafka twisted away from Sunny’s strike simultaneously.

Two threats.

One rhythm.

She spun between them effortlessly, Saint’s blade glancing off her guard as Sunny’s attack cut nothing but empty space. Before Sunny could follow up, Kafka’s heel snapped backward, catching him squarely in the chest and launching him away.

He vanished into the shadows just as he hit the ground.

A faint, sharp curve of her lips, eyes gleaming with something just shy of sadism.

Then she made a decision.

Her blade slipped from her fingers.

The tachi spun upward, end over end, suspended momentarily in the air as Kafka planted her feet and drew her fist back.

Her thoughts sharpened.

She focused on a phenomenon known to anyone who had reached the level of Master or beyond — but not achieved by most.

Soul Resonance.

When the soul and body were fully fused, Essence was no longer merely fuel. It became expression. With a precise, explosive injection of Soul Essence into an attack — executed within a fraction of a second — it was possible to unleash force that scaled exponentially, as if one’s very soul were striking alongside the body.

Most could not control it, not even Kafka.

But thanks to the senses granted by her Aspect, she could make it seem as if she could.

Saint brought her shield up.

Too slow.

White sparks erupted as Kafka’s fist connected with Saint’s shoulder.

The impact was catastrophic.

The sound was not a crash, but an implosion, a thunderclap compressed into a single instant. Saint’s massive frame was blasted sideways, her shoulder detonating into fragments of shadow as her entire arm was torn clean off.

The Ascended Demon flew.

Her form destabilized midair, shadows unraveling violently before she was forcibly desummoned, her broken existence snapping back into Sunny’s Soul Sea to heal.

Kafka exhaled slowly.

She turned.

Sunny stood outside the shadows now, staring at her.

His expression was strange.

Kafka felt it then — the aftereffects of Soul Resonance. A pleasant, intoxicating high flooded her mind, stimulation surging through her prefrontal cortex. It was the part of the brain responsible for Essence control and Aspect usage, and when pushed to extremes, it rewarded its user with inspiration.

Many Masters and Saints discovered new techniques in this state.

Kafka did not.

She had already milked her Aspect dry, exploiting Soul Resonance until there was nothing left to refine.

Her heightened senses caught Sunny’s muttered words.

"I get it."

Kafka caught her falling tachi, fingers closing around the hilt as she dashed forward.

Sunny rushed to meet her.

Both moved simultaneously.

Kafka’s control of Essence became sharper, more intricate, riding the lingering high as she prepared to clash. Their swords were positioned perfectly to meet.

And then Kafka felt danger, the sensation was sharp, immediate, wrong.

Her eyes flicked away from him for just a fraction of a second, instincts screaming as she tried to identify the threat. Her blade still met Hail Sorrow perfectly...

And the world twisted.

At the point of contact, a black spiral bloomed.

It whirled violently, Shadow Essence collapsing inward as Kafka was hurled backward, boots carving molten lines through the rooftop as she slid to a halt. Her sword chipped, a jagged fracture running along its edge.

Kafka stared at it.

Then she sighed.

She looked up at Sunny, who stood with Hail Sorrow lowered, shadows coiling around him in unfamiliar patterns.

Of course.

Of course he could do that.

She supposed that people were just allowed to observe the flow Soul Essence to the point of replicating a phenomena that was supposedly impossible to perform on command — even for herself. Well, there was one man, but he was long dead.

’It was a little different, too...’

Must have been a difference in Essence composition. It was too smooth and... silky? Not like the violent flash of brightness.

’He’d probably call it a Shadow Resonance, since he likes to just attach that word to anything...’

Kafka laughed softly, shaking her head.

"A lady really can’t have her fun around here, eh?"

She met his gaze, eyes gleaming with something close to fond exasperation as she summoned a pair of submachine guns, causing Sunny to immediately step into the shadows.

That boy was definitely, without question, one of the three most unfair people she has ever met.

The barrels of her guns aimed towards the sky, and without even glancing... she squeezed the trigger.