For Mount Sagiri Giyu Tomioka was both his starting point and his final destination.
Giyu Tomioka, familiar with the place, led the Kocho Sisters into the deep, damp secret passage.
But his steps were much faster than usual, and his tone carried a sense of relief and elation.
Very good!!
Finally, I'm out of that hellish situation!
Tasks! Work! This is where men belong!
Hot springs, breakfast, Sister Alliance —to hell with all of that!!
Right now, all he wants to do is slay demons, work, and dedicate everything to the cause of peace for humanity!
He, Giyu Tomioka, the pillar of our work, officially goes live today!!
At the end of the secret passage was a heavy wooden door.
Giyu Tomioka stepped forward and tapped the door three times gently in a peculiar rhythm.
The door opened silently.
A completely different world unfolds before the Kocho Sisters.
This place is less a research institute and more a wonderful space that blends Japanese elegance with Western precision.
A faint scent of herbs wafted in the air, along with a barely perceptible whiff of blood.
One side of the room was a Western-style laboratory table filled with various glass flasks, test tubes, alcohol lamps, and microscopes—so many instruments that even the erudite Shinobu Kocho had never seen before.
On the other side, there were traditional tatami mats and paper sliding doors. A woman dressed in a purple kimono, with a gentle temperament and otherworldly beauty, was kneeling in front of the tea table, elegantly grinding medicinal herbs.
Her beauty was quiet and serene, with a touch of fragility, like a night-blooming cereus under the moonlight.
Just one glance is enough to make one feel tenderness from the bottom of one's heart, and dare not speak loudly.
"Miss Tamayo."
"Mr. Giyu, you've arrived."
The woman called "Tamayo" looked up and smiled gently at him. Her voice, like a clear mountain spring, instantly calmed his heart.
Then, her gaze passed over Giyu Tomioka and landed on the Kocho Sisters behind him. A barely perceptible look of surprise flashed in her eyes, but she quickly understood.
"Who are these two...?"
"Hey!! You! Who gave you permission to bring outsiders to disturb Tamayo!"
Before Tamayo could finish speaking, a hostile voice, sounding like that of a rebellious teenager, suddenly rang out from behind the paper sliding door beside her.
A boy with short green hair and fierce eyes, like a protective little wolfhound, darted out from behind the door, spreading his arms to block Tamayo and Giyu Tomioka.
The way he looked at Giyu Tomioka was filled with naked contempt and hostility.
"Miss Tamayo is so noble! Do you ordinary mortals think you can just see her whenever you want?"
"Especially with your expressionless face! Don't think that just because Miss Tamayo is polite to you, you can take advantage of her!"
"Yushiro!"
Tamayo's voice carried a hint of helpless reprimand, "Don't be rude to the guests."
"But! Miss Tamayo! He brought two more women with him! They don't look like good people at all!"
The boy, nicknamed "Yushiro," pointed at the Kocho Sisters, puffing out his cheeks and hurling the most offensive insults at them.
Giyu Tomioka:...
A "#" symbol slowly appeared on Shinobu Kocho's forehead.
The smile on her face began to look somewhat dangerous.
"Oh, little brother, are you talking about us?"
Kanae Kocho's reaction was more direct. She smiled and stepped forward, instantly exuding a gentle yet irrefutable aura.
"We are members of the Demon Slayer Corps, and we came with Giyu- san on the orders of our Oyakata-sama."
"And who are you? What gives you the right to point fingers at us?"
Yushiro was overwhelmed by Kanae's aura and subconsciously took a step back, but his loyalty to Tamayo quickly overcame his fear.
He stiffened his neck, about to retort.
"Yushiro, step back."
Tamayo spoke again, and this time, although her tone was still gentle, it carried an undeniable air of authority.
Yushiro trembled, as if he had heard a royal decree. The fierce expression on his face vanished instantly, replaced by an infinite loyalty that seemed about to bring him to tears.
He obediently stepped aside, but his eyes remained fixed on Giyu Tomioka, as if he were guarding against a thief.
"I apologize for making you all laugh,"
Tamayo smiled apologetically, then turned her gaze to Giyu Tomioka.
"Mr. Giyu, I have completed the preliminary analysis of the blood sample you left last time."
When serious matters are mentioned, everyone becomes serious.
Tamayo led them to the experimental table filled with sophisticated instruments.
She picked up a glass bottle containing a diluted, pale red liquid.
"Based on my research, Mr. Giyu, your blood does indeed possess an incredible power capable of killing demons."
As she spoke, she drew a drop of liquid with a dropper and pointed to a low-ranking One-Eyed Demon in the corner of the room, chained up and howling uneasily.
"However, this power is very unstable."
As she spoke, she precisely placed the drop of liquid onto the ghost's forehead.
"Sizzle-"
A soft sound, like boiling oil dripping into cold water.
The ghost let out an extremely shrill scream. Where the drop was applied, a puff of white smoke rose, leaving a small scar that looked like a cigarette burn.
Then...
And that was the end of it.
The ghost paused for a moment, then roared even more frantically, as if mocking the weak and feeble attack.
The air in the room was so awkward it seemed to freeze.
Shinobu Kocho:...
Kanae Kocho:...
Giyu Tomioka:...
This... is what they call "incredible power"?
This effect is worse than being scalded with boiling water.
"Cough cough,"
A hint of embarrassment flashed across Tamayo's face, and she quickly explained,
"As you can see, Mr. Giyu's blood loses its potency at an alarming rate after leaving his body."
"What I'm showing you here is the effect after just one hundred days. Its effectiveness against ghosts is... barely better than nothing."
In other words,
Shinobu Kocho instantly grasped the crux of the problem.
"Our biggest challenge right now is how to maintain, or even enhance, the activity of Mr. Giyu's blood after it leaves his body, right?"
"Absolutely correct."
Tamayo's gaze toward Shinobu Kocho was full of approval.
"I'm thinking,"
Shinobu Kocho walked to the lab bench, picked up a test tube, and carefully examined the liquid inside under the light. She was completely absorbed in her area of expertise, radiating confidence.
"If blood is frozen at low temperatures and then quickly thawed before use, would this maximize the preservation of its cellular viability?"
"Or, we could try adding an 'excipient,' a neutral, non-toxic, stable solution that can mimic the internal environment of the human body..."
"I tried ultra-low temperature centrifugation, but it didn't work well; the cell wall damage rate was still 80%."
"As for excipients, I'm trying to extract an alkaloid called 'Wistaria' from Wisteria. Theoretically, it can play a certain stabilizing role, but..."
"But its toxicity can antagonize the 'demon-killing factor' in the blood, right?"
"That's right! So we need a gentler medium that can act as a 'bridge'..."
Two brilliant female scientists with medical knowledge ahead of their time began an academic exchange in front of everyone, a battle of wits that no one else could understand.
Terms like "mitochondrial energy conversion," "reverse transcriptase inhibition," and "cell membrane permeability"...
A string of technical terms flowed effortlessly from their lips.
Giyu Tomioka stood to one side, completely dumbfounded.
He discovered that his calm and composed mindset had cracked once again.
His current mood is just like when he was at the breakfast table earlier, unable to understand what the village chief and the Kocho Sisters were talking about.
No, I was even more confused than I was back then.
At least, he could barely understand the words "hot spring," "knife," and "young people" from the conversation at the breakfast table.
Now, he felt like a mortal who had accidentally wandered into a meeting place of gods. He recognized each word individually, but when put together, he had no idea what it meant.
He glanced instinctively at Kanae beside him.
She was smiling gently at the two women who were having a heated discussion, her eyes filled with pride and satisfaction.
Noticing Giyu Tomioka's gaze, Kanae turned her head, winked at him, and mouthed silently:
"Impressive, right?"
Giyu Tomioka nodded silently.
He suddenly realized that he wasn't so important after all.
Once you've donated your blood, it seems like there's nothing more for you to do.
Just as he began to question the meaning of life, the academic seminar over there seemed to be coming to an end.
"... Therefore, conventional methods have reached their limit."
Tamayo made her final conclusion, and as she looked at Giyu Tomioka, her gaze became incredibly solemn.
"Unless... we can find a perfect 'culture medium' that possesses an almost infinite ability to divide itself and can contain the domineering power in your blood."
"Culture medium?"
Giyu Tomioka finally heard a word he could understand.
"Yes."
Tamayo nodded, and then uttered a bold hypothesis that made everyone present hold their breath.
"The blood of the Demon King, and the blood of the Twelve Kizuki."
"Their cells possess a near-eternal vitality."
"I have a theory: what if we could mix your blood with theirs in a specific ratio..."
"Perhaps, we can not only solve the problem of activity decay, but even create an ultimate weapon that can fundamentally threaten Muzan Kibutsuji."
The entire room fell into a deathly silence.
All eyes were on Giyu Tomioka.
This plan is insane.
Hunting the Twelve Kizuki?
That's an unattainable goal that countless predecessors in the hundreds of years since the Demon Slayer Corps was founded have risked their lives to achieve!
However, after hearing this, Giyu Tomioka remained silent for a short while.
His face showed neither shock nor fear.
He simply walked calmly to Tamayo, and then, slowly, extended his right arm.
How much do you need?
His voice was calm and composed, yet it carried an undeniable, resolute determination.
Looking into his clear yet resolute blue eyes, Tamayo understood.
The man in front of me didn't need anyone to persuade him.
His determination had long transcended words.
"I see."
Tamayo nodded solemnly and took out a brand-new set of blood-drawing equipment that she had prepared beforehand.
"Before you bring back the 'culture medium,' I will use your fresh blood to complete all the preparations."
"But, Mr. Giyu,"
Just before the needle was inserted into his vein, Tamayo looked up and, in an unprecedentedly serious tone, reminded him:
Please be extremely careful.
"The Twelve Kizuki are truly extremely dangerous."