CHAPTER 4: THE MASTER OF THUNDER

Elsewhere in the Infinity Castle—

The winding halls echoed with a sharp crackle. Not of lightning—but of footsteps. Zenitsu Agatsuma, once a quivering coward, now ran through the shifting shadows with eyes blazing gold and heart resolute. There was no more hesitation in his breath. No more fear in his bones.

And then—

He found him.

A familiar figure cloaked in the garments of a demon, standing beneath flickering lightning veins in the ceiling.

Kaigaku.

Zenitsu's former senior. Once a student of the same master—Jigoro Kuwajima. Now… a traitor. An Upper Moon.

Kaigaku smirked, folding his arms arrogantly.

"Still alive, Zenitsu? Hah… pathetic. You always were. Clumsy. Weak. Crying all the time."

Zenitsu didn't speak. His fingers quietly coiled around the hilt of his blade.

Kaigaku stepped forward, his tone darkening.

"You only ever mastered one form of Thunder Breathing. One. You're not even worthy of the style. And yet, he chose you. Gramps chose you. What a joke."

He spat on the ground.

Zenitsu's gaze darkened. His hands trembled—not from fear—but from rage.

"…Who told you," Zenitsu said softly, voice cracking with fury, "that I could only use one form?"

Kaigaku blinked, confused.

Suddenly—

CRACK!

Zenitsu vanished.

He reappeared behind Kaigaku in a flash of gold, his First Form—Thunderclap and Flash, Sixfold—already roaring through the air.

Kaigaku barely blocked in time, staggering back.

Then another—

Second Form: Rice Spirit.

Third Form: Thunder Swarm.

Fourth Form: Distant Thunder.

Fifth Form: Heat Lightning.

Sixth Form: Rumble and Flash.

Kaigaku was thrown into a defensive dance, sparks exploding across the battlefield. He had underestimated him.

Zenitsu wasn't just fast.

He was fury incarnate.

Suddenly, time seemed to slow. As the dust swirled, Zenitsu's eyes flashed—and a voice came to him.

"Zenitsu… I always believed in you. You can surpass even the limits of the heavens… Finish this, my boy."

Jigoro Kuwajima.

His beloved gramps. The man who raised him. Trained him. Believed in him when no one else did.

Zenitsu's blade radiated brilliant gold. His hair fluttered in divine wind.

Kaigaku backed away, panic rising in his throat.

"Wait—what is that form—?!"

Zenitsu raised his sword. Lightning crackled along the steel like a storm condensed into steel.

He whispered:

"Seventh Form: Honoikazuchi no Kami…"

A thunder dragon—divine and wrathful—formed from lightning behind him, coiling around his body.

And then—he disappeared.

One single slash.

One blinding strike.

Kaigaku's head fell.

His final expression wasn't anger.

It was shock.

"…Heh… so… you really… weren't… weak…"

Zenitsu stood over him, breathing heavy, sparks still flickering around his feet.

A tear rolled down his cheek.

"…Rest now, Gramps. I did it."