Late autumn morning mist shrouded the Ubuyashiki Estate, while the surrounding pines and cypresses rustled in the cold wind.
This was the absolute core of the Demon Slayer Corps, a forbidden area hidden behind layers of barriers and a wisteria forest.
Normally, aside from the Nine Hashira when summoned, few outsiders ever set foot here.
But today, the tightly sealed gate was pushed open without obstruction.
Rin walked along the pebbled courtyard path with his hands in the pockets of his wool coat, his pace relaxed.
Kochou Shinobu followed half a step behind him, her expression tense.
"Are you really sure about this?"
She lowered her voice, her brows slightly furrowed.
"The Master's illness is no ordinary ailment, but a bloodline curse that has plagued the Ubuyashiki Family for a thousand years. It is said to be divine punishment for giving birth to a monster like Kibutsuji Muzan. Every head of the family, without exception, dies before the age of thirty, their body consumed by festering decay. For centuries, countless renowned doctors, and even demons skilled in medicine like Lady Tamayo, have been helpless against it."
As the one in charge of the Butterfly Mansion, she knew better than anyone how terrifying that curse was.
It was not something medicine or surgery could solve, but a bottomless abyss where vitality vanished without a trace.
"Divine punishment?"
Rin let out a faint sneer and shook his head.
"There is no such thing as divine punishment in this world. It's nothing more than high-dimensional karma. Or rather, the existence of that trash, Kibutsuji Muzan, acts like a parasite, continuously draining the vitality of those who share his bloodline on a conceptual level. As long as it's a matter of energy consumption, there is no pit that cannot be filled."
As they spoke, they arrived at the master bedroom deep within the estate.
The Kakushi guarding the area recognized the Special Executive Officer and the Insect Hashira. They saluted respectfully and stepped aside.
The sliding door was gently opened from within.
Ubuyashiki Amane, her white hair framing a gentle face, stepped out carrying a basin filled with murky, blood-tinged water.
She froze for a moment upon seeing them, then bowed slightly.
"Lord Rin, Lady Shinobu. My husband's condition has worsened today. He has just coughed up blood, so he is unable to rise and greet you. I hope you will forgive him."
Her voice was filled with exhaustion and sorrow.
Through the gap in the door, Rin saw Ubuyashiki Kagaya lying on the tatami.
It had only been a little over a month since he last saw him, yet the spiritual leader of the Demon Slayer Corps had withered to little more than skin and bones.
The purple-red rot marks on his face had spread from his forehead down past the bridge of his nose, completely robbing him of his sight.
"Lady Amane, it's fine."
Rin did not bother with formalities. He stepped inside and sat cross-legged beside the tatami.
Hearing the movement, Ubuyashiki Kagaya struggled to turn his head. His unfocused, gray-white eyes still accurately faced Rin's direction.
"Rin-san… cough, cough… you've come personally today. Is there any news about Kibutsuji Muzan?"
His voice was weak, but the gentle warmth that felt like a spring breeze remained unchanged.
"Kibutsuji Muzan is in hiding. Don't expect him to show himself anytime soon."
Rin looked at the face ravaged by the curse, his tone calm.
"I didn't come here to deliver information. I came to cure your illness."
The air in the room froze.
Ubuyashiki Amane's hands trembled violently, and the basin tilted as water splashed onto the tatami.
She stared at Rin in disbelief.
Ubuyashiki Kagaya was also stunned. Then a bitter smile appeared at the corner of his lips.
"I appreciate your kindness, Rin-san. But this is the destined fate of my clan. There is no need to waste effort on my broken body…"
"Be quiet and lie still."
Rin cut him off mercilessly.
Ignoring the couple's shock, Rin slowly opened his eyes. His pitch-black pupils instantly turned blood-red, and the Eternal Mangekyō Sharingan, its hexagram pattern intertwined with three tomoe, began to rotate silently.
Within the Sharingan's heightened vision, the purple-red marks on Kagaya's face were no longer mere signs of decay.
They were clusters of cold, malevolent energy, clinging like maggots to bone.
These energies acted like countless invisible straws, deeply rooted within every cell of Kagaya's body, continuously draining his vitality.
"As expected. A karmic curse born from shared bloodline is essentially a one-way extraction of life force."
Rin grasped the root of the problem.
To break such a curse, ordinary treatment methods were naturally useless.
Because even if the existing corruption were removed, new decay would immediately grow along the bloodline.
To break it, one had to use higher-dimensional power to sever the connection at its root, while simultaneously infusing enough life force to reconstruct the body.
Yin Release and Yang Release.
"Shinobu, step back. Lady Amane, if you don't want your husband to die today, do not make a sound."
Rin's voice was low and commanding, carrying an irresistible authority.
Amane covered her mouth tightly, her eyes instantly reddening as she pulled Kochou Shinobu back into the corner.
Rin raised his right hand, holding it just an inch above Ubuyashiki Kagaya's face.
Hum—
A deep, cold black chakra surged from his palm.
This was the pure power of Yin Release.
It represented spirit, will, and all intangible aspects.
Under the Sharingan's control, the Yin Release chakra became like scalpels precise down to the molecular level, piercing beneath the skin along the marks on Kagaya's face and severing the black energy threads sustaining the curse.
"Ah—!"
Even Ubuyashiki Kagaya, who had always endured pain without losing composure, let out a suppressed groan.
The agony of severing a thousand years of karmic bloodline ties struck directly at the depths of his soul.
"Endure it."
Rin's reminder was cold and indifferent.
As the Yin Release scalpels peeled away the roots of the curse layer by layer, the chakra in his palm shifted.
The cold black glow was suddenly replaced by a radiant emerald light, like the rising sun breaking through dawn.
Yang Release. The power of the body, life, and creation.
The emerald-green life force surged like a reverse waterfall, pouring continuously into Kagaya's body that had long since been drained dry.
A miracle unfolded.
From the corner, Kochou Shinobu and Ubuyashiki Amane witnessed a scene they would never forget for the rest of their lives.
The purple-red decayed flesh on Kagaya's face, which no medicine could suppress, began to dissolve the moment it came into contact with the emerald light.
The necrotic skin turned into black ash and scattered, replaced by smooth, healthy skin regenerating at a speed visible to the naked eye.
His shriveled muscles filled out once more, and the labored breathing in his chest gradually steadied, growing strong and rhythmic.
Even his prematurely aged hair slowly regained a faint luster under the continuous nourishment of Yang Release.
What lasted only a few minutes felt like an entire century to those watching.
When the light in Rin's palm finally faded, the only sound left in the room was Kagaya's steady, even breathing.
"It's done. Open your eyes and see."
Rin withdrew his hand, casually picking up a towel from beside the tatami and wiping his palm as if brushing off invisible dust.
Ubuyashiki Kagaya's eyelashes trembled.
The gray-white, clouded eyes that had been completely blind due to the curse now regained their clarity and depth.
He slowly opened them.
His vision sharpened from a hazy blur into focus.
He saw the wooden ceiling, the black-haired young man sitting beside him with a relaxed expression, and his wife in the corner, covering her mouth as she wept.
"I… can see?"
Kagaya raised his trembling hands and touched his face.
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