Cheng Mo moved rapidly through the night-shrouded mountain forest.
His superhuman physique allowed him to tread lightly, almost soundlessly.
The only sound was the rustling of leaves as the night wind swept through the trees.
"Familiar function… Since it can contract with special creatures in this world, what about the indigenous people?"
A thought uncontrollably popped into his head.
"Talents like Lady Tamayo, who possesses top-tier medical knowledge and research capabilities, yet is confined to this world due to her identity as a demon—if they could follow me back to the present world with complete loyalty, or even to other worlds…"
This idea was extremely tempting.
A top-tier research assistant who was absolutely loyal and could be taken to any world by him would be invaluable.
But he quickly calmed down.
The contract conditions required over ninety percent loyalty, and perhaps even some kind of bond… Establishing such a relationship with indigenous people would be far from easy and involve too many complications.
He immediately thought of Tanjirou, Kochou Shinobu, and even Kyojuro Rengoku.
Building deep trust with them might be possible, but to turn them into absolutely loyal "familiars"?
The ethical and operational difficulties instantly made him suppress this somewhat restless thought.
"This matter… requires careful consideration; I can't rush it."
He shook off these jumbled thoughts and refocused his attention on the current objective.
The immediate priority was that demon with special energy.
"Black Feather."
He silently gave the command through the soul link.
"Master."
Black Feather's response came immediately.
"Reconfirm target's location and status."
"Yes."
Black Feather, high in the sky, once again focused its perception on that valley.
"The target's energy source location has not changed in the slightest; it remains in an absolutely static state."
"Master, it's very strange. Based on my observations of the surrounding area, this target has shown no signs of activity recently… possibly for a very long time, and has no record of harming anyone."
Cheng Mo frowned slightly.
A demon, remaining absolutely still at night, neither hunting nor moving?
This abnormal phenomenon simultaneously heightened his doubts and interest.
"Maintain surveillance, plan the shortest route."
"Understood. The optimal path has been marked for you."
Following the topographical map directly transmitted into his mind by Black Feather via the soul link, Cheng Mo quickly reached the valley located deep in the mountains.
Cheng Mo reined in the flickering electric arcs around him, reducing the operation of his Thunder Breathing to its lowest maintenance state.
Like a seasoned hunter, he silently approached the cave hidden behind the waterfall.
The closer he got to the cave entrance, the more pronounced the chill in the air became.
It wasn't just simple low temperature; it carried a bone-chilling, spirit-freezing cold (yin-leng, cold and gloomy) sensation.
Even the roaring sound of the waterfall couldn't mask that deathly silent atmosphere.
The faint golden glow of the Eye of Truth silently swirled in Cheng Mo's eyes.
He "saw" it: a pale blue energy dust, invisible to the naked eye, permeated the cave entrance, slowly breathing in and out like a cold breath.
They intertwined with the natural energy flow of the mountain, yet they were completely out of place.
It was like a piece of ice forcibly embedded into living tissue, constantly emitting waves of repulsion and chaos.
He stepped into the cave.
The cave was unusually dry, a stark contrast to the moisture from the waterfall outside.
The rock walls were chillingly cold to the touch, covered with a thin layer of white frost.
The deeper he went, the darker the light became, and the lower the temperature, so much so that his exhaled breath instantly turned into white mist.
The passage twisted downwards, and he walked for about fifteen minutes.
Suddenly, it opened up.
A huge natural grotto appeared before him.
In the center of the grotto stood an enormous, Dark blue (you-lan-se, deep blue) ice crystal that almost touched the cave ceiling.
The ice crystal was astonishingly clear, with no impurities inside.
It emanated visible waves of chilling cold, enveloping the entire grotto in a hazy, icy blue glow.
And within the ice crystal, a figure was unmistakably sealed.
It was a young girl dressed in old, tattered clothing, vaguely discernible as a miko (shrine maiden) outfit.
Her eyes were tightly closed, her face pale, yet her delicate features were still visible.
The girl's hands were clasped over her chest, as if she had fallen into an eternal slumber.
The powerful chill emanating from the ice crystal, and a chaotic yet forcibly restrained energy fluctuation, originated from her.
Cheng Mo's gaze sharpened, and he slowly stepped forward.
He tried to observe the girl in the ice crystal more closely.
Just as he was less than ten meters from the ice crystal—
"Please… please don't come any closer!"
A faint, anxious, clearly tearful girl's voice, without any warning, sounded directly in his mind.
Cheng Mo's footsteps suddenly halted, and the lightning around him instinctively threatened to erupt!
His hand pressed against the startled insects at his waist, and the Eye of Truth instantly went into full power mode.
His sharp, eagle-like gaze quickly swept every corner of the grotto.
Rock walls, dome, deep shadows… no one.
Besides him and the girl in the ice crystal, there was no sign of life, nor any hidden energy source.
The voice seemed to have appeared out of thin air.
"I-I'm sorry… I scared you…"
The voice sounded again, still tearful and filled with deep fear, broken and intermittent.
"Powerful swordsman… please… leave here… leave quickly…"
"My sister and I… we finally managed to seal ourselves away… we can't go out again…"
Cheng Mo forcibly suppressed the instinct to immediately attack or retreat, maintaining extreme calm.
He stood still, his gaze fixed on the girl in the ice crystal, and spoke in a steady voice: "Who are you? Where are you?"
It was both a question and a test.
"I… I am Hotaru…"
The voice in his mind seemed to calm down a tiny bit because of his response, but it was still full of tension.
"Kamiya Kawayuki Hotaru… I… I don't have a body now… My sister and I… we are together…"
"Together?" Cheng Mo caught the strange word.
"What do you mean? Who is your sister? Is it this person in the ice crystal?"
"Y-yes…" The voice calling herself Hotaru choked.
"My sister is Yuki… Kamiya Kawayuki… We… we weren't like this originally…"
Under Cheng Mo's calm guidance, the girl's soul named Hotaru, intermittently and incoherently, began to recount their past.
It was a long time ago, during the Edo period.
They came from a small shrine family that had guarded the spiritual pulse (mai, pulse, vein/pulse) of this deep mountain for generations.
Her sister, Yuki, was the miko (shrine maiden) of this generation, possessing rare spiritual power.
Although she could only vaguely sense natural energy and purify minor impurities.
She was gentle yet resilient, burdened with the duty of guardianship.
Her younger sister, Hotaru, was lively and cheerful, and deeply admired her sister.
Although she herself had no spiritual power, she always happily followed her sister, helping out.
However, disaster struck one night.
Kibutsuji Muzan attacked the shrine.
Her sister, Yuki, stepped forward to protect her sister and the shrine, but was utterly powerless to resist.
Ultimately, she was injected with Muzan's blood.
Driven by the initial madness and man-eating hunger of demonization… the newly transformed sister, with her consciousness muddled, influenced by Muzan's will, attacked and… ate her only sister, Hotaru.
Perhaps it was due to the faint trace of spiritual power remaining in her sister, the bizarre characteristics of Muzan's blood, and the powerful, distorted obsession of her sister Hotaru, who, before dying, "didn't want to leave her sister."
The soul of her younger sister, Hotaru, did not dissipate but was completely integrated into her sister Yuki's demon body in an incredibly peculiar, almost cursed way.
From then on, two souls resided within one body.
Under Muzan's control, her sister Yuki's demon body, relying on this eerie "dual-soul" characteristic and the special power brought by her own spiritual power, grew continuously stronger, committing countless acts of slaughter.
More than a hundred years ago, when she was active, her name was the terrifying nightmare of countless Demon Slayer Corps members—
Upper Rank Two, Yuki-onna.