Kokushibo had never intended to kill Rengoku Shinjuro.
Of all the humans he had encountered, Shinjuro was one of the few he regarded with genuine respect.
But circumstances had changed.
If Shinjuro reported Tamayo to the Demon Slayer Corps, then her existence already precarious would become impossible to maintain.
To the Corps, she was still a demon.
To Muzan, she was a traitor.
If either side found her first, everything Kokushibo had been quietly building would collapse.
More importantly
That unseen presence.
That oppressive, intangible gaze that had haunted him for years… had grown sharper.
Closer.
He could no longer afford uncertainty.
There was only one path forward.
Shinjuro had to die.
And in his place
Kyojuro Rengoku would inevitably rise.
Shinjuro stared at Kokushibo's revealed form, disbelief and regret warring in his eyes.
Six eyes.
The unmistakable markings
Upper Rank One.
The strongest of the Twelve Kizuki.
Second only to Muzan Kibutsuji.
"…Iwakatsu…"
The name felt bitter on his tongue now.
Yet the hesitation lasted only a moment.
His grip tightened.
His resolve hardened.
"I will defeat you."
Flames surged.
Flame Breathing, Second Form: Rising Scorching Sun!
A blazing upward slash tore through the night, its arc fierce and precise.
Kokushibo stepped back fluidly, evading the strike with minimal movement.
Then
He countered.
Moon Breathing, Sixth Form: Perpetual Night, Lonely Moon – Incessant!
A storm of crescent blades erupted outward, layered and relentless, forming a suffocating web of slashes.
Shinjuro's expression sharpened.
He pivoted instantly.
Flame Breathing, Fourth Form: Blooming Flame Undulation!
Flames spiraled around him in a defensive vortex, deflecting the incoming crescents in a burst of heat and sparks.
The ground cracked beneath the clash.
Kokushibo's gaze flickered brief, but genuine.
"…Impressive."
Shinjuro's strength far exceeded that of most Hashira.
For a fleeting moment, Kokushibo recalled the future
What Kyojuro might one day become.
But that future would never come to pass if tonight failed.
Moon Breathing, Second Form: Pearl Flower Moongazing!
Twin arcs of curved blades descended with deceptive elegance.
Shinjuro twisted aside, narrowly avoiding a fatal strike but thin crescent wounds still carved across his side.
Blood flowed.
"…So this is the power of an Upper Rank…"
Even so
He did not retreat.
Flame Breathing, Third Form: Blazing Universe!
A powerful downward strike cleaved forward, flames roaring like a collapsing star.
Kokushibo raised his blade to intercept
The impact scorched even him.
But Shinjuro did not stop.
Flame Breathing, Fifth Form: Flame Tiger!
A ferocious, tiger-shaped torrent of flames surged forward, driven by sheer will.
The force of it pressed against Kokushibo's blade, causing even his stance to shift slightly.
For a moment
The battlefield trembled.
Kokushibo's lips curved faintly.
"…Good."
It had been a long time since he had exchanged blows like this.
A worthy opponent.
A worthy friend.
Then
He became serious.
Moon Breathing, Seventh Form: Mirror of Misfortune – Moonlit Reflection!
His blade extended grotesquely, transforming as it cut.
A massive sweeping strike shattered the ground, crescent blades scattering across a wide radius.
The technique forced distance
Control.
Shinjuro evaded the core of the attack
But a crescent sliced across his abdomen.
The gap between them widened.
And that gap… was fatal.
Shinjuro steadied himself.
Then
His breathing changed.
Calm.
Silent.
Even his presence seemed to fade.
Kokushibo's six eyes narrowed.
Through the Transparent World, he saw it
Muscles compressing.
Coiling.
Like a drawn bowstring.
Then
Release.
Flame Breathing, First Form: Unknowing Fire!
A single, explosive dash.
Too fast.
Even Kokushibo
Fully focused
Was grazed.
A thin line opened across his neck.
For the first time
He was struck cleanly.
"…Not enough!"
Shinjuro forced his body further.
Beyond its limits.
His footing broke
But he adapted instantly.
Using one hand against the ground, he twisted his entire body mid-motion
Reversing direction.
Striking from behind.
Flames surged once more
But this time, they curved.
A full arc.
A blazing crescent mirroring the moon itself.
Flame Breathing, Tenth Form: Blazing Crescent Dragon!
A technique born in desperation.
Unrecorded.
Unrefined
Yet brilliant.
The strike landed.
Several flesh-blades protruding from Kokushibo's body shattered instantly.
For a moment
Silence fell.
Kokushibo exhaled slowly.
"…That was extraordinary."
His voice held no mockery.
Only acknowledgment.
"A feint into acceleration… followed by a complete directional inversion."
He stepped forward.
"If not for my physiology…"
"…you might have killed me."
But Shinjuro
Was finished.
His body gave out.
His blade struck the ground as he collapsed, breathing ragged and shallow.
Still
His eyes remained clear.
"…Why…"
"…Why did you come into my life?"
There was no hatred in his voice.
Only
A quiet need for truth.
Kokushibo stood over him.
For a long moment
He said nothing.
Then
"…If you had never discovered Tamayo…"
His voice lowered.
"…I would have remained your friend."
Silence.
"…But I cannot allow you to speak of her."
A pause.
"You were… the one man I respected among humans."
Shinjuro closed his eyes.
A faint, weary smile touched his lips.
"…Then… that is enough."
Kokushibo raised his blade.
No hesitation.
No cruelty.
Only resolve.
"Father, we're back!"
The voice shattered the moment.