BOOM—!
Amidst thunderous roars, eerie black lightning coiled around Kaigaku's body, and his formerly dark golden Nichirin Blade was now covered in sinister black patterns.
"[Thunder Breathing—Fourth Form: Distant Thunder]!"
Kaigaku, his entire form crackling with black lightning, lunged at Emiya with overwhelming force, hurtling toward him like a devastating storm.
A razor-sharp slash cleaved toward Emiya.
"[Sword Breathing—Thunder Form: Thunderclap and Flash]!"
The next moment, Emiya, gripping his Nichirin Blade tightly, erupted with a fierce golden lightning storm of his own.
Clang! Clang! Clang—!
Ahead, a cascade of sparks burst forth, accompanied by relentless, crisp ringing as their blades clashed repeatedly.
Golden lightning intertwined chaotically with black, illuminating the battlefield as Emiya and Kaigaku engaged in a fierce exchange at speeds beyond human perception.
"First Form?! You know the First Form too?! GRAAAAHHHH!"
Kaigaku suddenly recalled his human past, enraged by how closely Emiya's sword technique resembled the first form of Thunder Breathing.
The first form—Thunderclap and Flash—was the most fundamental technique of Thunder Breathing, yet it was the only form Kaigaku had never mastered.
His inability had once earned him ridicule from fellow Demon Slayers, fueling his deep-seated envy of Agatsuma Zenitsu.
Suddenly, Kaigaku's black lightning intensified explosively.
"[Thunder Breathing—Second Form: Rice Spirit]!"
Compared to Emiya, who had only barely scratched the surface of Thunder Breathing, Kaigaku's technique was undeniably superior.
Moreover, Kaigaku was no longer human. His newfound demonic powers only amplified his strength to monstrous levels.
Whoosh!
In that blindingly fast world, Kaigaku's black lightning shredded through the air with an ear-splitting shriek, slicing toward Emiya.
This was a series of five lightning-shaped rapid strikes, executed simultaneously.
Emiya's breath hitched sharply, his pupils constricting in alarm.
Humm—!
The air around him surged violently, transforming into spiraling gusts of wind that wrapped protectively around Emiya's body.
At the same instant, the terrifying five-strike barrage of hellish black lightning closed in, leaving no room for escape.
"[Sword Breathing—Beast Form: Whirling Fangs]!"
Emiya's voice echoed resolutely within the enveloping darkness. His other hand swiftly grasped another Nichirin Blade, shaped like a beast's fang, which appeared seemingly from nowhere.
Hiss!
A sound like water splashing fiercely against stone erupted. A fierce whirlwind suddenly burst from the surrounding black lightning, piercing through it like a spear, aimed straight at Kaigaku, who had just unleashed his technique.
"Excellent! Excellent! Let me see your limit! You must taste absolutely delicious!"
Facing Emiya's ferocious, spinning assault resembling a raging whirlwind, Kaigaku cackled madly, brandishing his Nichirin Blade.
BOOM!
A world-shaking collision exploded between savage lightning and a swirling silver vortex, unleashing a shockwave of wind and lightning in all directions.
Floors and walls splintered violently, shredded like paper fed into a grinder.
"AGAIN!!!"
Kaigaku, brutally smashed through multiple wooden structures, shook off blood spilling from wounds inflicted by razor-like wind blades.
Once again, violent thunder cracked the air.
Kaigaku's figure dissolved once more into pitch-black lightning.
Emiya, however, was clearly in much worse shape following the brutal impact.
His wounds took the form of jagged lightning-shaped gashes, searing him with intense pain that significantly impaired his fighting capabilities.
This was Kaigaku's Blood Demon Art, enhancing his blade's sharpness and imbuing his lightning with ominous darkness. Each strike tore flesh brutally, leaving lightning-shaped wounds that burned with extreme heat, tormenting victims continuously.
Such pain would easily overwhelm an ordinary person's mental fortitude.
But was Emiya an ordinary person?
"[Sword Breathing—Thunder Form: Thunderclap and Flash]!"
Gritting his teeth, Emiya's form became golden lightning once again.
BANG!
Another savage collision resounded, generating heart-clenching booms and waves of wind scattering violently.
To any observer, the battle between Emiya and Kaigaku appeared evenly matched, a fierce exchange of blows that shook the soul.
Yet Emiya knew all too clearly—his skills and strength paled compared to Kaigaku.
And now he faced a demon with limitless regeneration.
The wounds Emiya had struggled desperately to inflict healed instantly, even the torn clothes reforming seamlessly.
Meanwhile, Emiya's own condition deteriorated rapidly. Pain shot through his body like rogue lightning, his legs numbing dangerously with each passing second of combat.
Did this mean Emiya's defeat was inevitable?
Absolutely not.
Almost every demon shared the same fatal flaw—arrogance. They viewed themselves as superior beings, casually dismissing humans as mere ants they could crush effortlessly. Even when facing capable opponents, they rarely took the threat seriously.
Only at the brink of death did demons finally unleash their true power.
This arrogance was precisely why many Demon Slayers, despite being weaker, managed to defeat vastly stronger demons.
Emiya, however, gave every fight his all. He was determined not only to kill demons, but also to survive—not merely for himself, but for those who had always watched over him. He refused to perish quietly here.
He was waiting.
Waiting for the moment Kaigaku revealed a critical opening.
Clang!
The metallic ring of colliding blades echoed once more in the chaotic corridor.
"You're really a pain. Is this generation's Mizunoto Demon Slayer's really this strong?"
Kaigaku stared in disbelief at Emiya, bloodied yet defiantly upright, deeply questioning the authenticity of the low-level "Mizunoto" rank embroidered clearly on Emiya's uniform.
It was supposed to be the Demon Slayer Corps' weakest rank—mere cannon fodder sent into battle, much like Genin from Konoha Village.