Meiji 41 (1908) — Early Summer
Butterfly Estate & Elsewhere
The slayer's name was Haru.
He was supposed to die.
Everyone knew it—including him.
Lower-ranked, newly promoted, sent with two others to clear a minor infestation near a river village. The demon turned out faster than expected, tougher, smarter. One companion died instantly. The other was dragged screaming into the trees.
Haru ran.
The demon caught him.
Claws pierced his side. Bone cracked. He remembered the smell of rot, the laughter—
And then—
Bang.
The sound was wrong. Too sharp. Too sudden.
The demon jerked.
Not stopped. Not killed.
But slowed.
Confused.
Its regeneration stuttered, veins darkening where the bullet had pierced.
Haru didn't think.
He swung.
Nichirin cut through the neck while the demon was still screaming in confusion.
Silence followed.
Haru collapsed beside the body, gasping, alive in a way that felt… unreal.
Later—at the Butterfly Estate—when Kanae finished checking his wounds, he whispered to everyone who would listen:
"…If that bullet hadn't slowed it… I'd be dead."
The words spread.
From bed to bed.
From estate to headquarters.
From whispers to certainty.
> "There's a place you can rest."
"There's a weapon that buys you time."
"There's a Sun Hashira who doesn't let you die."
Rumors grew wings.
---
Casualty reports changed.
Not dramatically.
Not yet.
But enough.
Commanders noticed that certain patrols—especially those equipped with experimental ammunition—returned with fewer body counts.
More injured.
More alive.
Some veterans scoffed.
"Luck."
Others whispered.
"Hope."
And then there were those who began asking—quietly—
"Can my unit be assigned near the Butterfly Estate?"
---
Far away.
In shadows untouched by wisteria.
A Lower Moon knelt, head bowed, blood pooling beneath his hands.
"…My Lord," he hissed. "Reports are… inconsistent."
Muzan's fingers tapped once.
"Inconsistent how?"
"…Humans are not dying as expected."
Silence.
Another demon spoke, voice trembling. "Encounters end faster. Resistance lasts longer. Some survive wounds that should—"
Crack.
The speaker's head snapped sideways, body crumpling.
Muzan rose slowly.
"Do not confuse inconvenience with threat," he said coldly. "Lower Moons exist to be replaced."
Still—
His eyes narrowed.
"…But investigate."
Fear rippled through the remaining demons.
For the first time in decades—
Humans were not just surviving.
They were adapting.
---
Late night.
The Butterfly Estate was quiet except for one building still lit.
Inside—
Shinobu stood over a worktable covered in notes, vials, and bullet casings. Her brow was furrowed, irritation sharp in her movements.
"This reaction curve makes no sense," she muttered. "It should suppress regeneration faster."
Across from her, Kai rolled up his sleeves.
"May I?"
She paused—then nodded.
"Fine. But don't sugarcoat it."
He examined the notes.
For a moment, he was quiet.
Then—
His breathing slowed.
The world… shifted.
---
Great Sage — Active
Not with spectacle.
With clarity.
Information aligned. Variables reordered. Cause and effect snapped into place like puzzle pieces long forgotten.
Kai's eyes sharpened—not glowing, not dramatic—just focused.
"The carrier oil destabilizes too quickly," he said calmly. "It burns off before full absorption."
Shinobu blinked.
"…That's—wait. That would explain the delayed onset."
Kanae, who had entered silently, leaned in. "Can it be fixed?"
"Yes," Kai replied immediately. "Wisteria base alone is insufficient. It needs a secondary inhibitor—something that slows diffusion without weakening poison."
Shinobu stared at him.
"…You sound like you've never left this place."
He smiled faintly. "I didn't. Just… took a longer route."
She scoffed, but there was fondness in it. "You always do this. Disappear into sword nonsense and come back acting like a scholar."
Kanae laughed softly. "He worked here longer than most attendants."
Shinobu exhaled, then nodded sharply. "Alright. Help me refine it."
---
Hours passed unnoticed.
They worked shoulder to shoulder like they always had—no hierarchy, no ceremony.
Shinobu adjusted measurements.
Kai recalculated dosages.
Kanae recorded results, occasionally stopping them before exhaustion turned dangerous.
"This compound," Shinobu said, pointing, "increases paralysis but reduces lethality."
Kai shook his head. "Too risky. Slayers need certainty."
"…Then this?"
"Better. Pair it with heat-resistant casing."
Shinobu's eyes lit up. "You're right. That could stabilize the reaction on impact."
She paused, then added quietly—
"…I missed this."
Kai didn't look up. "Me too."
Great Sage faded—not abruptly, but gently—leaving behind conclusions instead of strain.
On the table lay a revised formula.
More efficient.
More merciful.
More deadly—to demons.
---
By morning, the first improved batch was ready.
Shinobu held a bullet up to the light, eyes sharp and satisfied.
"This one," she said, "will hurt."
Kai nodded. "And buy time."
Kanae smiled. "That's all most slayers need."
Outside, the estate stirred awake.
Patients stretched. Attendants moved. Life continued.
And somewhere—
A demon hesitated for half a second longer than it should have.
That half second—
Was enough.
---
(Note - Grate Sage is mostly Dorment now. It will activate sometimes. After all even Grate Sage need fule to continue working. And this world don't have magic. So it's mostly Dorment collecting energy. I don't wanna make Kai too reliant on His cheat)