The name Tsugikuni Yuko had in her previous life no longer mattered, because in this life, she was Tsugikuni Yuko.
As the eldest daughter of the Tsugikuni family, she had two older twin brothers above her.
Her eldest brother was Tsugikuni Michikatsu, and her second brother was Tsugikuni Yorichii.
That's right—she had transmigrated.
She had transmigrated into the world of Demon Slayer.
Even though Yuko hadn't followed the anime closely in her past life, Demon Slayer's overwhelming popularity meant she still came across related clips from time to time. Its beautiful animation and effects were attractive enough that she eventually got interested herself.
However…
She seemed to have arrived too early.
Yuko had only watched one season of the anime, and had only occasionally come across short videos about Tsugikuni Yoriichi.
The most famous line, of course, was: "What is the value of a life to you?!"
But if she wasn't mistaken, her second brother—Tsugikuni Yoriichi, the absolute peak of Demon Slayer's power—was a character who lived hundreds of years before the story began.
Which raised a serious problem:
How was she supposed to survive until the story actually started?
"Sigh."
Yuko, who had a wooden flute hanging around her neck, propped her cheeks in her hands and sat on the steps with a troubled expression. She watched her eldest brother, Tsugikuni Michikatsu, practice swordsmanship with their teacher below, her feet swinging absentmindedly.
"Yuko, don't sit like that. You need to keep good posture."
Her mother, Akeno, called out from behind. Yuko turned to see her second brother, Tsugikuni Yoriichi, leaning tenderly against Akeno as they walked over.
"Mother."
Yuko quickly shifted from her lazy posture into proper seiza—something she still hadn't quite gotten used to.
Her mother in her previous life had been a lazy gambler who wasted all their assets and showed little care for the family. She was the sort of person Yuko found very hard to respect, much less love.
So she had absolutely no defense against someone as gentle as Akeno.
Once she was sitting properly, Yuko exhaled in relief and waved at the second brother nestled beside their mother. "Yo, Yoriichi."
Who would've thought the legendary peak of power was such a clingy, spoiled kid when he was young?
But before she could blink, Akeno flicked her hard on the head. "How many times must I tell you? Call him 'Elder Brother'!"
"Yes, Elder Brother." Yuko rubbed her aching head, not noticing the momentary flash of pain in Akeno's eyes.
Akeno was gentle, but when she got angry, it was always unexpectedly frightening.
Yoriichi only responded to his unruly little sister with a soft smile.
A gentle mother, a gentle brother, and a cute little sister—these were Yoriichi's most precious treasures.
He helped Akeno sit beneath the veranda while Yuko sat with them. He himself walked over to join his brother Michikatsu to watch the lesson.
Their father's retainer, who was teaching Michikatsu swordsmanship, noticed Yoriichi standing quietly nearby and handed him a wooden sword, smiling as he encouraged him to try.
Michikatsu—sweaty, exhausted, and sore all over from being beaten during practice—finally got a moment's rest.
"Mother, Yuko."
He walked over and looked up at them.
"Brother~" Yuko greeted him with a bright smile, then immediately turned her focused gaze back to the training grounds.
Michikatsu's brows furrowed almost imperceptibly. He glanced back toward Yoriichi. He didn't believe his weak little brother could last more than a few moves against their father's retainer.
After all, he—with all his talent and effort—had never won a single match.
But in the next instant, to everyone's shock, Yoriichi—who had only just been taught how to hold the sword—launched a storm-like attack, moving with impossible speed.
In the blink of an eye, he brought down a full-grown man.
Michikatsu was left utterly stunned. Akeno's lips parted slightly in disbelief. Only Yuko wore an expression of "as expected."
Truly the peak—at seven years old, he wielded strength unimaginable for a normal person.
While the others reeled in shock, Yoriichi simply stared blankly at the bamboo sword in his hands.
He hated the feeling of striking another person's body.
He dropped the sword and quietly returned to the veranda.
Michikatsu finally snapped out of his daze and rushed to sit beside him. "How did you do that?"
Yoriichi lowered his eyes and answered softly, "When someone prepares to attack, their lungs always move sharply. All you need to do is watch the direction of the bones, the contraction of the muscles, and the flow of blood."
"…"
Michikatsu was dumbfounded. He had no idea what his little brother had just said.
Akeno's eyes flickered faintly.
This child… Yoriichi's eyes could see the divine.
Yuko's eyes sparkled. She knew exactly what this was!
It was the pinnacle of a swordsman—no, of martial arts.
The Transparent World.
The ability to see the opponent's weaknesses, their attack patterns, and to conceal one's own presence.
Practically x-ray vision.
"Let's stop talking about swordsmanship," Yoriichi said softly. "I want to play sugoroku and fly kites with Brother and Yuko instead."
Originally, he had wished to become the second-strongest samurai in the country, but the unpleasant sensation of striking someone's body made him abandon that dream entirely.
Michikatsu lowered his head, his hands on his knees secretly clenched.
Yuko patted his shoulder jokingly. "Don't be so tense all the time. Relax once in a while."
Michikatsu brushed her hand away without hesitation and left without even saying goodbye to their mother.
Yuko let out a long breath.
She knew it.
She didn't know much about the future storyline, but she had seen short clips showing Yoriichi's brother becoming the strongest demon under Muzan.
Upper Rank One — Kokushibo.
As for the fans calling him a "six-eyed lemon spirit," she hadn't understood back then, but now… it was starting to make sense. (Lemon = sour = jealousy)
Good. She was definitely going to correct this boy's twisted mindset!
She believed she could do it. After all, she had been a college student in her past life.
How hard could it be to guide a child?
…
However, before she even had the chance to fix Michikatsu's personality—
One night, not long after—
"Yuko."
Yoriichi's voice woke her from her sleep. She slid open the door, rubbing her eyes groggily.
"What is it, Yoriichi?" she yawned. "Are you scared to go to the bathroom alone?"
Her usual nonsense drew the same calm expression from Yoriichi—but this time, it was tinted with sorrow.
"Mother has passed away."
"…Eh?"
Yuko was instantly awake.
Akeno…
Yuko opened her mouth but couldn't form words.
"You can ask Mother's attendants for the details," Yoriichi said quietly. "I'm going to say goodbye to Brother now."
"Goodbye?"
"I'm leaving for the temple."
Only then did Yuko notice the travel pack by his side.
Their father was a superstitious man. Among the twins, Yoriichi—born with strange marks—was treated as ill-fated and insignificant. If not for Akeno's protection, he would've been killed at birth.
In contrast, the treatment between Michikatsu and Yorichii was so different it felt like the gap between master and servant.
From food to clothing to education, they lived in entirely different worlds.
As the abandoned one, Yoriichi had always been destined to go to a temple at age ten.
To become a monk.
But… both Michikatsu and Yorichii were only seven years old now.
And she herself was only six.
Yuko suddenly thought of the scene where Yoriichi defeated their father's retainer.
Their father needed an heir who could support the family. With Yoriichi's overwhelming talent revealed, the brothers' positions must have reversed.
Was Yoriichi leaving early to avoid harming Michikatsu?
While Yuko was lost in thought, Yoriichi said, "Yuko, I'm leaving."
"Take care of yourself."
He picked up his pack and prepared to go.
"Wait."
The words slipped out of Yuko's mouth.
Yoriichi paused and looked at her.
But when it came time for Yuko to speak, her mind went blank.
Tell him to stay?
He was only seven…
But he was already strong enough to defeat adults, far stronger than she was.
Her silence was answered with a gentle smile