It wasn't until late one night that Mr. Cheng Mo quietly left his hiding place in Asakusa.
Inside the cold cave, time seemed to stand still.
The colossal ice crystal still towered there, emanating an eerie chill and dead silence.
Mr. Cheng Mo silently infiltrated and stood before the ice crystal.
After nearly a month of diligent cultivation with the Heart and Soul Secret Canon, his soul power was no longer what it once was.
The Eye of Truth activated once more, a faint golden shimmer flowing as his vision penetrated the solid ice, reaching straight to its core.
The scene he witnessed now was far clearer and more profound than the last time.
Kamiya Kawayuki's soul aura, which should have been pure, was still tightly entwined by a thin but extraordinarily stubborn layer of dark red impurity, like a maggot clinging to bone.
That was precisely the manifestation of Muzan's soul fragment.
Not only was it on the surface, but some delicate, tendril-like energy threads had already become deeply intertwined with her own soul's origin, attempting to take root.
However, beside that contaminated aura, a faint but exceptionally clear and resilient ice-blue spiritual light was tightly nestled with another, even smaller, yet radiating incredibly soft and warm light.
The two auras were like fledgling birds huddling together for warmth in a storm, stubbornly resisting the erosion of the dark red impurity, guarding the last sanctuary.
That soft light, clearly belonged to Kamiya Kawayuki's sister, firefly (Hotaru).
"The fragment's stubbornness and penetrative ability are higher than expected, and its entanglement with the origin is extremely deep, making detachment very difficult, but fortunately..."
Mr. Cheng Mo thought to himself, his gaze sweeping over the dark red fragment.
Its energy level was indeed very low, far lower than the fragment's activity in the Upper Rank demon blood.
This was primarily because Kamiya Kawayuki had discarded most of her demon blood, and she herself was sealed, unable to provide enough 'fuel' to nourish it.
The success rate… was higher than anticipated.
He did not act rashly.
Instead, he slowly closed his eyes, condensing his newly refined and enhanced mental power into an extremely slender, gentle yet resilient thread.
He carefully avoided the dark red contaminated areas and once again touched the soft light representing Hotaru.
This time, his contact directly reached Hotaru's soul.
"Hotaru, it's me, Mr. Cheng Mo."
His thoughts were transmitted.
The soft light clearly trembled, sending back a wave of extreme surprise and caution: "Mr. Cheng Mo? You… you can directly… contact me now?"
She clearly remembered that when Mr. Cheng Mo came last time, although his aura was powerful, he still couldn't communicate directly with her soul's core so clearly.
This leapfrog improvement gave the message he had brought earlier, "a method has been found," an unprecedented level of persuasiveness.
"Yes, I've had some breakthroughs on the soul level."
Mr. Cheng Mo's thoughts were also very steady.
"That's why I'm confident in coming to you both; a method has been found, and we can attempt to strip that curse from your sister."
"But the process will be extremely painful for both of you, and there are risks. I need your full cooperation."
The soft light was silent for a moment, then transmitted an incredibly firm wave.
"I'm not afraid of pain. As long as my sister can be freed, whatever it takes! Mr. Cheng Mo, please… begin. What do I need to do?"
Hotaru was very excited; the century of waiting seemed to finally see a glimmer of hope.
Mr. Cheng Mo's mental response was calm and clear, like a surgeon's final instructions before an operation:
"What you need to do is become the final anchor for your sister's consciousness. While I operate, use your soul perception to guide me, helping me avoid her soul's most core, most fragile areas."
"Most importantly…" he emphasized, "no matter how painful the process, you must find a way to keep her last shred of consciousness awake."
"Once her consciousness completely sinks due to the pain, that fragment might seize the opportunity to retaliate, or even completely devour her remaining origin."
Without hesitation, Hotaru's thoughts instantly echoed back, with a resolve almost like a burning flame: "I understand, I will definitely do it, Mr. Cheng Mo, please begin!"
That will to protect, willing to give everything for her sister, was pure and warm, even causing Mr. Cheng Mo's mental power to subtly fluctuate.
He said no more.
Mr. Cheng Mo sat cross-legged on the cold, hard cave floor, operating the techniques of the Heart and Soul Secret Canon.
His breathing became long and deep, adjusting his spirit, will, and control over Lightning Release Chakra to an unprecedented peak state.
The Eye of Truth operated to its extreme, perceiving the most minute entanglements within the souls inside the ice crystal.
He saw a more complex truth.
Hotaru's soul was indeed the root of Kawayuki's endless pain, reminding her every moment of the sin of devouring her closest kin.
But on the other hand, Hotaru's own obsession of "not wanting to leave her sister" and "wanting to protect her sister," as well as the existence of her soul power, acted like a shield, to some extent helping Kawayuki resist the complete erosion of Muzan's fragment that "annihilates humanity."
It was this extremely contradictory state that allowed Kawayuki to regain some humanity at the last moment and choose the desperate path of self-sealing in ice.
And now, Muzan's fragment was not only deeply rooted in Kawayuki's soul but also formed some complex connection with Hotaru's soul, like a malicious vine simultaneously entwining two interdependent trees.
Forcibly stripping the fragment would very likely inevitably severely damage or even tear Hotaru's soul!
Even if successful, if Kawayuki awakened to find her sister had completely vanished to save her, the outcome might be even more cruel than being eternally frozen.
An extremely bold, almost impossibly demanding plan formed in his mind.
He needed to first use his own refined and powerful mental energy, supplemented by the newly improved serum inhibitor that could temporarily reduce the fragment's activity.
He would untie the entangled nodes between Hotaru's soul and Muzan's fragment, separating them as much as possible to create an extremely tiny, operable surgical space.
Within the created tiny space, he needed to utilize the ultimate mental control brought by the Heart and Soul Secret Canon, with the Eye of Truth's soul vision as real-time navigation.
Then, he would combine his highly condensed mental power, which simultaneously contained "purification" characteristics and ultimate "precision" control, with a wisp of Chakra tamed to its extreme, forming an invisible "soul scalpel."
This blade must precisely burn and sever only those "malignant tissues" belonging to Muzan's fragment that connected to Kawayuki's soul origin.
At the same time, it must, with extremely high precision, carefully avoid all healthy "blood vessels and nerves" connected to Hotaru's soul.
The process was more perilous and prolonged than anticipated.
Fine beads of sweat permeated Mr. Cheng Mo's forehead, his mental power depleting at an unprecedented rate.
Every second felt like walking a tightrope over a bottomless abyss.
His invisible "soul scalpel" carefully probed inward.
Bit by bit, it pried and peeled away the countless tiny connection points between the fragment and Kawayuki's soul origin.
Each time a connection point was severed, the colossal ice crystal would emit a nearly imperceptible, subtle tremor.
Inside, the frozen Kamiya Kawayuki, even in her unconscious state, would let out an extremely faint, yet profoundly painful moan, as if her soul was being forcibly torn apart.
"Sister… hold on… it'll be over soon…"
Hotaru's thoughts continuously came through, filled with pain and urgency, yet she struggled to remain stable.
While constantly encouraging and comforting her intensely suffering sister with her thoughts, she exerted all her effort to guide Mr. Cheng Mo: "Mr. Cheng Mo… a little to the left… ah… there… close to me… please avoid… Yes! That connection point below… that's the fragment's!"
Her guidance helped Mr. Cheng Mo navigate the incredibly complex and dangerous labyrinth of the soul, painstakingly avoiding one trap after another, precisely locating the targets to be excised.