Fate's Slave - Shadow Slave X Honkai Star Rail

Sunny walked away from the ruined stretch of the Stargazer Navalia without looking back.

His pace was unhurried, boots clicking softly against alloy plating as the ambient hum of the port settled back into something resembling normalcy. Overhead, damaged infrastructure groaned as automated systems began their slow, methodical repairs.

His mind was still racing, not with danger or lingering tension, but with exhilaration.

The fight replayed itself in his thoughts, not as a sequence of events, but as a web of realizations. Every clash, every instinctive decision, every reckless experiment he had conducted in the middle of a Saint-level battle had yielded something tangible. His Aspect had not grown stronger. It had unfolded.

Boosting his Shadow Creatures had been the simplest discovery, but no less important for it. Their strength, resilience, and even the potency of their Abilities responded directly to how much Shadow Essence he was willing to invest. He had treated them like static summons before, fixed entities with defined limits. That assumption had been wrong. Even the speed of their recovery could be altered, although with a steep cost in Essence.

They were truly extensions of him, deserving to be Shadows to the last remnant of their God.

The second realization had been more subtle, but far more profound. Shadows he manifested into the real world were not just constructs. They were pathways. By combining Shadow Step with Shadow Manifestation, he had turned creation into opportunity, using his constructs — both intact and fading back to simple shadows — for mobility rather than as mere objects.

The main flaw of Shadow Step was that shadows only existed on a pre-existing surface. However, if the shadows could become the surface themselves, then that gave Sunny much more room to play around.

And then there was the most unusual experiment of all.

Imbuing himself with the Abilities of his Shadow Creatures.

Summoning Nightmare into his Soul Sea instead of the real world had been an impulse, driven by instinct rather than logic. The result had exceeded his expectations and confirmed his suspicions. Shadow Creatures were not merely companions or tools. They were repositories of power that he could selectively tap into, overlaying fragments of their Abilities onto himself.

The cost had been severe. His Essence reserves had bled away at an alarming rate, and the tradeoff was absolute. While he borrowed an Ability, that Shadow could not be summoned normally. Worse, many of their Abilities were designed to complement one another, forming layered effects that lost efficiency when isolated.

Essentially, this part of his Aspect was useless outside of extremely nuanced scenarios.

The [Mantle of Fear] alone had been enough to disrupt Kafka, even briefly. Scaled to Sunny’s own strength, it had bypassed Rank disparity entirely. The absence of Nightmare’s Attributes stung, but it taught him the limitations he had. If they weren’t Shadow Abilities, he couldn’t use them.

And then there was the technique.

Sunny’s grin widened slightly as he replayed the moment of impact in his memory. The way his Essence had collapsed inward before detonating outward. The way it had resonated through his body, his soul, and his mind all at once. It had not felt like a normal attack. It had felt like striking reality itself.

And as with all great things, it required a name.

Fortunately, the infinitely-expanding number of Sunnys that have ever existed, would exist, and could exist, can settle their differences when it came to a couple of things.

One of those was that their naming abilities left nothing to be desired!

’Well, the first word has to be shadow. The second, is... attack! But it’s also super... no, more than super! It’s a... Super Duper Shadow Attack!’

Not only had it been exponentially stronger than any normal blow he could produce, but it had done something else entirely. It had stimulated him. Forced his senses into alignment. Accelerated his understanding mid-combat in a way that bordered on absurd. If that was what simply timing the application of Essence could do, looking into other ways to use his Shadow Essence would be a worthwhile endeavor. It was nice of Kafka to show him a spectacle, even if it had severely wounded Saint.

He had copied it instinctively.

Just like that.

The thought sent a thrill through him that he did not bother suppressing.

Sunny exhaled slowly, shadows rippling faintly at his feet as his mind wandered further down increasingly dangerous avenues. What would happen if he turned himself fully intangible? Not just stepping through shadows, but becoming one. If his body were rendered shadow, could he then use Shadow Manifestation on himself?

The possibilities spiraled outward, branching endlessly.

He reined them in with effort.

Experimentation could wait. For now, he had people to regroup with.

He felt them long before he saw them.

His shadow sense had expanded after Ascending, seemingly beyond twenty kilometers, its range now so vast that it blanketed the entire Stargazer Navalia without effort. Every shadow, every obstruction, every movement registered in his perception as naturally as breathing — although, he had to make an effort to not be overloaded with information, only focusing on anything that he believed required his attention.

He followed the sensation and rounded a corner.

March, Welt, and Tingyun stood amid a cluster of unconscious Cloud Knights, their bodies neatly arranged in what looked suspiciously like an improvised rest area. March was gesturing animatedly as she spoke, Welt listening with his usual mild patience, while Tingyun smiled politely, tail swaying as if none of this concerned her.

Sunny stopped a few meters away and stared.

Then he stomped forward, boots striking the ground with deliberate emphasis.

”Wow. Looks like you three were having plenty of fun.”

March flinched, then turned, eyes lighting up when she saw him.

”Oh! You’re done already?”

Sunny raised an eyebrow.

”Yeah. Might have been over faster if I had some help.”

March laughed awkwardly and rubbed the back of her head.

”Well... you looked like you had things under control. And you did! So I figured I’d just, you know, let you cook.”

Welt adjusted his glasses and gave Sunny an apologetic look.

”Youthful conflicts should be resolved by the youth themselves. Besides, I am rather old.”

Sunny stared at him.

”...You were literally standing ten minutes away.”

Welt smiled faintly and said nothing.

Tingyun clasped her hands together and tilted her head.

”And I’m just a mundane Foxian, after all. What could I possibly do against a Stellaron Hunter? Cheer you on?”

Sunny’s eyes narrowed as he looked at her.

”Who knows? Maybe you could have suplexed her or something.”

She only laughed.

March blinked, before sending a concerned look towards Sunny.

”Uh... now that I think about it, where is Kafka? Wasn’t this a capture mission? You didn’t... you know?”

She made a gesture against her own neck, making the message clear.

Sunny pretended to look offended.

”What do you take me for?! She’s alive and... alive. The Master Diviner did most of the work in taking her down, and is also taking her away.”

Welt studied him for a long moment, eyes searching Sunny’s face as if trying to piece together a puzzle with missing pieces. Then he spoke again.

”Did you forget? We were supposed to listen in on the questioning.”

Sunny blinked.

”We were?”

March deadpanned.

”Sunny, you were literally there when we talked to Jing Yuan about this.”

He stared at her blankly.

”...Was I?”

March crossed her arms.

”Yes! You nodded and everything!”

Sunny paused, then shrugged.

”Maybe I forgot.”

March squinted at him, clearly unconvinced, but Welt only sighed.

”It happens. Let us regroup, then.”

Tingyun clapped her hands together.

”Well then! Since the danger has passed, shall we move along?”

The three of them turned and began walking.

Sunny followed a step behind, then slowed.

He leaned his neck forward slightly as shadows crept up, partially obscuring his face. His eyes darkened, sharpening as his thoughts shifted from exhilaration to calculation.

Something rustled under his clothes, before the head of an obsidian-scaled Serpent peaked out from under his sleeve — its size much smaller and convenient, barely able to wrap around his forearm. It’s dark eyes peered at him, showing a small semblance of curiosity.

Sunny gently rubbed his pinky finger over its head.

He had been willing to ignore what he saw, but... it seemed he needed to be more constricting.