Kaigaku's body turned into a streak of black light and vanished instantly.
In Tanjiro and Inosuke's eyes, a golden flash and a black flash collided, erupting into a blinding explosion of light.
Then, the black light completely devoured the golden one.
Zenitsu's figure was sent flying out of the radiance.
"Zenitsu!"
"Zentaro!"
Tanjiro and Inosuke rushed forward and caught him before he hit the ground.
At this moment, Zenitsu's entire body was charred black. The collision of their ultimate speeds had shattered the bones in his sword arm; his skin was bruised and blood-red.
Under normal circumstances, Zenitsu would have already been screaming in pain, whining, and ready to give up.
But now, he bit down hard, silent, his eyes locked unwaveringly on Kaigaku in the distance.
Kaigaku let out a cold laugh, mocking,
"With a human body, your speed has already reached its limit. You'll never surpass it. But since you are my junior disciple, I'll give you an opportunity. Become a demon like me. Only as a demon can you reach the pinnacle of power."
A smirk tugged at the corner of his mouth.
"But as an offering of loyalty, you'll have to kill your two companions and bring me their heads."
"Zen'taro is my underling!" Inosuke roared furiously. "And I'll be the one to protect my underling!"
"Beast Breathing, Second Fang: Slice 'n' Dice!"
Driven by rage, Inosuke crossed his twin blades and lunged, slashing in an intersecting strike.
But to Kaigaku, Inosuke's speed was no faster than a turtle's crawl.
"Thunder Breathing, Second Form: Rice Spirit!"
Before Inosuke's blades could even reach him, Kaigaku unleashed five lightning-shaped strikes in rapid succession.
Luckily, thanks to his sharp instincts, Inosuke managed to dodge in time, escaping with only minor injuries.
To cover Inosuke, Tanjiro also launched his attack.
"Hinokami Kagura—Clear Blue Sky!"
Tanjiro swung down from above, his circular slash wrapped in flames.
Among the three, the only one Kaigaku truly considered a threat was Tanjiro's Hinokami Kagura.
When Kaigaku had once faced Higurashi Yoriichi's Sun Breathing on Mount Sagiri, it felt like staring into the face of his natural enemy—an overwhelming, despairing fear.
Even though Muzan Kibutsuji's blood had regenerated his severed arm, the scar left by Yoriichi's blade never healed.
Now, as Tanjiro's flaming blade approached, that same deep-rooted terror stirred again within Kaigaku's heart.
He could have counterattacked—but instead, he chose to retreat cautiously.
Kaigaku's withdrawal created an opening for Inosuke.
"Beast Breathing, Ninth Fang: Extending Bendy Slash"
Inosuke lunged in, his twin blades whipping forward with all his might.
Kaigaku feared Tanjiro, but not Inosuke. Calmly, he raised his Nichirin Blade and blocked the attack with ease.
"Gotcha, idiot!" Inosuke jeered. Then, exploiting his extraordinary flexibility, he dislocated his joints mid-attack, extending his reach to deliver a surprise strike.
Caught off guard, Kaigaku was slashed across half his head.
Excited, Inosuke shouted, "Santaro! Now's your chance!"
Inosuke's unpredictable move opened the window Tanjiro needed.
"Hinokami Kagura—Dance of the Fire God: Dragon Sun Halo Head Dance!"
Tanjiro's movements became like a blazing dragon, flames surging as he closed in.
Facing that intense heat, Kaigaku quickly retreated.
"Sixth Form: Rumble and Flash!"
A storm of lightning blades shot toward Tanjiro, trying to halt his advance.
But Tanjiro's body erupted in fierce flame—he didn't defend, he didn't slow down. He charged straight through.
Kaigaku's thunder strikes struck him squarely, but the Sun Breathing flames dulled their power, leaving only shallow wounds.
Kaigaku continued to back away. Just as Tanjiro's blade was about to strike—
Kaigaku suddenly rolled to the ground, grabbed a handful of sand, and flung it into Tanjiro's eyes.
Tanjiro had been keeping his eyes wide open the entire time to track Kaigaku's movements. But when the sand hit, his instincts took over—he blinked.
That single blink gave Kaigaku his chance. He kicked the momentarily blinded Tanjiro, sending him flying.
"You coward!" Inosuke shouted, stomping furiously.
Kaigaku sneered,
"Heh. As long as I win, what does it matter if it's cowardly? History is always written by the victor."
Tanjiro finally cleared the sand from his eyes and regained his sight.
Beside him, Zenitsu—dragging his swollen, broken arm—stood shoulder to shoulder with Tanjiro and Inosuke once more.
"Tanjiro, Inosuke—I found his weakness!" Zenitsu said, his voice firm. "When Kaigaku uses that lightning-speed sword technique, it shares the same flaw as Thunderclap and Flash."
Inosuke tilted his head. "What flaw?"
"In that instant of acceleration, he can't change direction," Zenitsu explained. "And his right arm—his sword arm—doesn't move smoothly.
Master Yoriichi once said he severed Kaigaku's arm with Sun Breathing. So it's very likely that arm never healed completely."
Inosuke frowned. "But he's so fast! How do we even hit him?"
Zenitsu took a deep breath. "I'll take the lead. You and Tanjiro watch for the opening—and finish him when it appears."
"But, Zenitsu—your arm…" Tanjiro said, concern in his voice.
Zenitsu shook his head. "I'll be fine. I'm using my breathing to suppress the pain. It's only my arm that's injured—my legs are fine. As long as I can withstand his attacks, I'll be okay. You just need to end it when the moment comes!"
Before Tanjiro or Inosuke could object, Zenitsu shouted,
"I'm the only one fast enough to keep up with him! Let's go!"
"Thunder Breathing, First Form—Thunderclap and Flash: God Speed!"
Seeing Zenitsu unleash God Speed again, Kaigaku responded in kind—
"Final Thunder—Lightning Flash Reversal!"
In the heart of Ōsumi Village, two lights—one golden, one black—clashed and intertwined in a blinding storm.
Tanjiro and Inosuke held their breath, searching desperately for a flaw, a break, any chance to strike.
But the speed was beyond human sight.
All they could do was stare, helpless and tense, as the two streaks of light collided again and again, their brilliance filling the night.