Tokitō Muichirō found himself in a strange, dreamlike space.
Standing before him was a boy who looked almost exactly like him.
The boy grabbed Muichirō by the collar and shouted angrily,
"Why did you join the Demon Slayer Corps?! Don't you know that fighting demons could get you killed?!"
As Muichirō looked into the boy's face, tears began streaming uncontrollably down his cheeks.
He rubbed at them with trembling hands and murmured,
"What's happening to me? Why am I crying... even though I don't remember you?"
"Still haven't remembered, have you?" the boy said sharply.
"I'm your older brother — Tokitō Yūichirō! Now answer me! Why didn't you live the way I wanted — safely and peacefully?!"
Yūichirō's tone was harsh and filled with anguish.
In that instant, Muichirō's lost memories came flooding back.
He finally remembered — the boy standing before him was indeed his brother, Tokitō Yūichirō.
Fragments of his past life began to replay vividly in his mind.
Muichirō had once lived in a poor family that made a living cutting wood.
Though life was harsh, the four of them — father, mother, and the two brothers — were happy together.
But tragedy struck when their mother contracted pneumonia.
Their father went out during a typhoon to gather medicinal herbs for her, only to fall from a cliff to his death.
Their once-happy family of four was suddenly torn apart.
All that remained were the two brothers — Yūichirō and Muichirō — who had only each other to rely on.
Yūichirō shouldered the responsibilities of an elder brother, doing his utmost to care for Muichirō.
Their quiet, fragile life continued — until one day, a visitor arrived and changed everything.
The visitor was Amane Ubuyashiki, the wife of the Corps Leader.
She came to tell the brothers that their ancestors had been famed swordsmen — users of the original Breathing Style — and invited them to join the Demon Slayer Corps.
But before Muichirō could even respond, Yūichirō furiously drove her away.
Amane visited several more times, but Yūichirō always turned her away, even once dousing her with cold water.
Because of this, the brothers quarreled.
They stopped speaking for a while, and Yūichirō grew increasingly cold and sharp-tongued,often scolding his brother as useless, even saying,
"'Mu' in Muichirō stands for 'mu' in munō — 'incompetent.'"
The following summer, fate struck again.
A demon appeared at their home.
Yūichirō, harsh as he always seemed, immediately stepped in front of his younger brother to shield him.
In an instant, the demon severed Yūichirō's arm and gravely wounded him.
Muichirō screamed in fury.
Overcome with rage, he fought the demon, dragging it outside and pinning it to the ground with wooden stakes.
He held it there until the sunlight burned it to ash.
But Muichirō was also badly wounded.
When he exhausted the last of his strength and crawled back home,
he found Yūichirō lying on the floor, barely breathing.
Yūichirō, despite his own injuries, reached out and pulled his dying brother into his arms.
Muichirō's breath was faint, barely there.
Yūichirō wept and prayed desperately:
"Buddha... please, save my brother. He's such a kind soul... please..."
Though he had never believed in gods or Buddha, Yūichirō blamed himself for everything.
All he wished was for his little brother to live.
In his final moments, Yūichirō finally spoke his true feelings,
his weak, trembling voice filled with love and regret.
"I know now... The 'Mu' in Muichirō doesn't mean 'nothing.'
It means infinity — infinite potential... the power to protect others without end."
Hearing his brother's final words, Muichirō at last understood Yūichirō's love — and his guilt.
Perhaps through Yūichirō's heartfelt prayer, Muichirō survived.
But because of his wounds and the trauma of that night, he lost all of his memories.
When Muichirō finally regained his memories,
he looked at his brother through tear-filled eyes and whispered, voice trembling,
"Brother... I've missed you so much."
Yūichirō looked at him, unable to hide his sorrow.
Still, he hardened his heart and asked again,
"Why, Muichirō? Why did you join the Demon Slayer Corps? Why didn't you live the safe, quiet life I wanted for you?"
Muichirō answered earnestly,
"Brother, I was born to seek happiness.
In the Demon Slayer Corps, I found my purpose — my place — and my responsibility.
So please... support me."
Feeling the sincerity in his brother's words, Yūichirō's heart softened.
He embraced Muichirō tightly, voice breaking as tears fell.
"I just... didn't want you to die in danger, Muichirō... that's all I ever wanted."
At that moment, their parents appeared, wrapping both sons in a warm embrace.
Yūichirō's mother spoke gently,
"Yūichirō, believe in Muichirō. He's bringing happiness to others now. You should be proud of him."
Yūichirō wiped his tears away and, with his usual pride, said,
"Muichirō, don't you dare die too soon.
Without your constant noise, I've finally gotten some peace and quiet!
Now hurry up and get going!"
A shining light appeared in the strange space.
Muichirō, though reluctant, began walking toward it step by step.
Watching his brother's retreating back, Yūichirō couldn't hold back one last shout:
"Muichirō! You must live on — live well!"
Muichirō nodded firmly.
"I will, brother. I promise."
He passed through the light — and his consciousness returned to his body.
His once-lifeless eyes regained their glow.
With heartfelt sincerity, Muichirō turned to Kokushibō and said,
"Thank you... for helping me regain my memories — for letting me see my family again."
Kokushibō looked deeply into Muichirō's eyes and asked,
"Muichirō, would you like to learn the Moon Breathing?"
"Moon Breathing?" Muichirō asked in surprise — he had never heard of such a style.
Kokushibō explained,
"The Moon Breathing is a derivative of the Breath of the Sun — one of the original Breathing Styles.
Though it cannot surpass the Sun's power, it is stronger than any of the five fundamental Breathing Styles that stemmed from it."
Muichirō's expression hardened with resolve.
"I'll learn it. If it can help me slay demons and bring others happiness — I'll master it!"
Kokushibō smiled in quiet satisfaction.
"To think... after hundreds of years, I have finally found my successor."