Infinity Castle.The final battle.
"Huff… huff…"
Blood streamed down Tanjiro's cheeks, staining his vision a deep crimson.
His body had long since reached its limit. The hands gripping his sword trembled uncontrollably. Forcing his eyes wide open, Kamado Tanjiro glared at the kimono-clad figure standing before him.
Tsugikuni Mitsuba.
She was born in the distant Warring States era, the younger sister of the legendary "Child of God," Tsugikuni Yoriichi, and twin brother Tsugikuni Michikatsu.
She stood as Upper Rank One of the Twelve Kizuki, the only inheritor of the Child of God's swordcraft, the strongest demon in existence next to Kibutsuji Muzan, and the nightmare that had haunted the Demon Slayer Corps for centuries.
Inside the small dojo shaped by Nakime's Blood Demon Art, severed limbs and broken bodies of Demon Slayers lay strewn across the floor.
Some were people Tanjiro recognized.Others, he did not.
Tsugikuni Mitsuba…
How many swordsmen have you stopped here?How many of my comrades have you slain?
They… they…
"Urrraaaah!"
Faces of his fallen companions flashed violently in Tanjiro's mind. Rage and grief crashed over him in a single breath. Tears blurred his vision as he roared and charged at the woman before him once again.
He had to win.He must win.
He had to kill her.He would kill her.
Years earlier, in a gentle morning of the Warring States era, sunlight warmed the earth.
In the town governed by the Tsugikuni family, a girl named Tsugikuni Mitsuba hurried along the corridor of the family estate.
She stopped before a small room tucked into the corner of the courtyard. Glancing left and right to make sure no one was nearby, she quietly opened the low wooden door and crawled inside.
"Yoriichi, look. Mother made this hairpin for me."
The room was empty and cramped. On a futon in the corner, the boy who had been lying silently and staring at the ceiling slowly sat up and turned toward her voice.
His eyes were clear yet unfocused. His long, deep-red hair draped over his shoulders, and on the left side of his forehead rested a strange flame-shaped birthmark.
This was Tsugikuni Yoriichi, Mitsuba's second older brother.
Yes… Mitsuba was a reincarnator.
In her previous life, she had been born frail and sickly, enduring years of suffering before quietly passing away on a hospital bed.
When she opened her eyes again, she found herself reborn as a baby into the noble Tsugikuni clan.
It was a prestigious family. Her father was a daimyo ruling a prosperous town, and her mother Akeno was the daughter of another powerful lord.
Mitsuba was the youngest child and the only daughter. Before her were the twin brothers: the eldest, Tsugikuni Michikatsu, and the younger twin, Tsugikuni Yoriichi.
A family of five. Wealth and honor. Two healthy brothers. A mother who smiled warmly. A body free of the illness that had chained her past life.
For Mitsuba, it was the kind of dreamlike happiness she had never dared to hope for.
If there was anything less than perfect, it was only the fate of the twins.
In this era, twins were seen as an inauspicious sign that could spark disputes over succession.So when Yoriichi was born with a strange mark on his forehead, their father had once considered killing him at birth.
Only thanks to Mother Akeno, who threw herself forward in desperate protection, did Father relent. He declared that Yoriichi would be allowed to live until age ten, after which he would be sent to a temple to become a monk.
And so, Yoriichi was permitted to remain in the Tsugikuni household… in name only.
In daily life, despite being a son of the clan, Yoriichi received none of the education or care given to Michikatsu, who was raised as the rightful heir.His treatment was even poorer than Mitsuba's.
He lived in this small, dilapidated corner room, wore coarse robes, and was forbidden from leaving the estate freely.
It was because of this that Mitsuba had, from a very young age, often sneaked to this little room to talk with Yoriichi.
Sometimes Michikatsu would come as well.
The three siblings would sit together, reading, practicing writing, playing sugoroku, and talking about the future.
Most of the time it was Mitsuba and Michikatsu doing the talking. Yoriichi simply stared with those clear, hollow eyes, occasionally replying with a single quiet word.
Mitsuba had long since grown used to it.
"Here, Yoriichi, look at this."
Kneeling beside him, Mitsuba gently removed the jade hairpin from her hair and held it up.
It was carved from smooth green jade, the ornamental head shaped into three delicate leaves.
"Mother said these three leaves represent my name and the three of us siblings.
The middle leaf is me, and the two on the sides are Michikatsu and you.
Even if the two of you are separated for now, as long as I'm here to connect us, we will always be united.
Only if we support each other will we be happy, and only then will the Tsugikuni clan continue to prosper.
What do you think, Yoriichi?"
Although Yoriichi did not speak, he still smiled faintly and gave the smallest nod.
"Oh, right! There's also this."
Like performing a magic trick, Mitsuba pulled something from her sleeve.
A pair of Hanafuda earrings.
"Mother made these for you.
She said they carry all the prayers she has offered to Amaterasu Omikami on your behalf. They will surely protect you for life."
She pushed the earrings gently into Yoriichi's hands, then stood and offered him her own.
"All right, Yoriichi. Let's go. Father is out inspecting the town today, so Mother told me to bring you to breakfast."
Because Father despised Yoriichi, the family was forbidden to approach him when Father was home. Even at mealtimes, Yoriichi was forced to eat alone in this tiny room.
Only on mornings like this, when Father was away, could the siblings sit together.
"Hya! Ha! Again!"
"Well done, young master Michikatsu. Please continue!"
Just as Yoriichi stood and took Mitsuba's hand, shouts from the courtyard echoed through the estate.
Curious, Yoriichi tilted his head and, after a long moment, asked his first question of the day.
"What is elder brother doing?"