"I'LL KILL YOU BOTH! I'LL PROVE I'M THE STRONGEST!"
"I'll send you both to hell to join that old man!"
"Grandpa didn't favor us," Zenitsu said quietly. "He wanted us all to be pillars, together."
"Thunder Breathing, Fifth Form: Heat Lightning!"
He slashed upward, a massive bolt of heat and corrupted electricity tore through the floor, aiming for Zenitsu.
Zenitsu vanished.
"Thunder Breathing, First Form: Thunderclap and Flash."
ZAP.
He cleared the lightning in a single breath, closing the gap instantly. He aimed for the neck, but Kaigaku parried at the last second he is an upper rank for a reason.
"TOO SLOW!" Kaigaku roared. "Sixth Form: Rumble and Flash!"
A corrupt storm of lightning bolts rained down, surrounding Zenitsu, pinning him in place.
Manjiro, leaning on the railing, flicked his wrist.
"Snake Muffler."
The bandages from his outfit shot out like vipers, wrapping around Zenitsu's waist and yanking him out of the kill zone a fraction of a second before the black lightning scorched the spot where he stood.
Manjiro stepped forward, "Watch closely, Kaigaku, don't blink cause you will miss it" Manjiro said.
He raised his hand which held nothing.
"Thunder Breathing, Fourth Form..."
The pressure dropped.
"...Distant Thunder (Hamon Enhanced)."
CRACK-BOOM.
It wasn't the corrupt black lightning of a demon. It was pure, golden lightning manifested through Hamon. It replicated Kaigaku's technique perfectly, but the output was the same, if he had infused it with his weapon, it would have tripled.
The blast hit Kaigaku square in the chest.
"GAAAAH!"
The Upper Rank was slammed into the back wall, cratering the wood. Smoke rose from his chest, his regeneration stalling as the Hamon burned his cells.
"HOW?!" Kaigaku shrieked, peeling himself off the wood, his eyes wide with terror. "THAT'S MY ENHANCED TECHNIQUE! THAT'S A BLOOD DEMON ART! HUMANS CAN'T DO THAT!"
"You sold your soul for power," Manjiro said coldly, walking forward. "You ate people. You betrayed Gramps. And for what? I just replicated your 'ultimate power'"
He looked down at the demon. "I could have killed you with that. Do you know why I didn't?"
Kaigaku trembled. "Why... why mock me?!"
Manjiro didn't answer. He just looked at him with empty, pitying eyes.
Furious, humiliated beyond reason, Kaigaku rushed in.
"Thunder Breathing, Second Form: Rice Spirit!"
Five rapid slashes.
Manjiro weaved through the attacks with his hands in his pockets.
Moon Breathing footwork.
Kaigaku froze. That movement. It was exactly like him. Like Kokushibo.
The realization hit him: Zenitsu wasn't lying. He really defeated Upper One.
"Why... Why... Why..." Kaigaku said as his mind was breaking apart. "Why does he have everything?!"
Manjiro stopped dodging. "You've eaten so many people," he said, voice devoid of emotion. "Can you even tell right from wrong anymore?"
"I DECIDE WHAT'S RIGHT!" Kaigaku yelled, trying to hide his trembling. "I AM SPECIAL!"
"If that's your answer," Manjiro sighed. "So be it."
Kaigaku turned his blade on Zenitsu, desperate for an easier target. He couldn't beat Manjiro. He knew that now. But he could kill the crybaby.
"Use it!" Kaigaku screamed, egging him on. "Use your only technique, master's pet! You can't beat me with just the First Form!"
Manjiro stepped back. As he felt the same sensation, an instinct as if someone was calling for help.
Tamayo.
He looked at the bridge. Then at Zenitsu.
He appeared behind Zenitsu, whispering into his ear.
"I will leave it to you, pikachu."
Then, Manjiro vanished.
Godspeed.
He was gone, leaving a streak of golden light in its path racing toward where he sensed help.
Kaigaku laughed, relief washing over him. "He left! He left you! He left you to die because you're weak!"
Zenitsu didn't look back at Manjiro. He locked blades with Kaigaku, then shoved him away, creating space.
He crouched. The stance for the First Form.
"Predictable!" Kaigaku screamed. "I know your timing! I know your breath!"
He intercepted Zenitsu, knocking him back. He followed up immediately. "Third Form: Thunder Swarm!"
Lightning cut Zenitsu from all angles. Zenitsu bounced off a wall, blood spraying.
"Eightfold!"
Zenitsu dashed eight times. Kaigaku blocked every single one, his superior speed and reaction time overwhelming the younger slayer. On the final strike, Kaigaku blasted him back with a wave of black lightning.
Zenitsu hit the floor, sliding back.
"It's over!" Kaigaku prepped his Heat Lightning again, red and black electricity crackling around him. "How does it feel to be inferior?"
Zenitsu stood up.
He dropped into a low stance, lower than the First Form. His hand hovered over his sword, but his breathing changed.
Kaigaku paused. "What is that stance? Grandpa never taught that!"
"He didn't," Zenitsu said. Steam curled from his mouth. His eyes opened, glowing with intense focus. "This is my form. I created it. I wanted to use it alongside you."
"Kaigaku's eyes widened. "What...?"
"DIE!" Kaigaku swung his sword, unleashing a storm of death.
"Thunder Breathing, Seventh Form..."
Zenitsu launched.
"...Honoikazuchi no Kami." (Flaming Thunder God)
FLASH.
A golden dragon of lightning consumed the room. It moved faster than the eyes could see. Faster than sound.
It tore through Kaigaku's neck before he could even blink.
SLICE.
Kaigaku stood there, sword raised.
Then, his head slid off his shoulders. It spun through the air, his expression frozen in shock.
The golden dragon faded. Zenitsu stood behind him, his haori fluttering in the wind of his own speed.
Kaigaku's body crumbled to ash.
Zenitsu slowly sheathed his blade. The click of the guard hitting the sheath echoed in the silence.
"Sorry, Grandpa," he whispered.
He looked up at the ceiling, tears in his eyes. "Aniki... did I do good?"