Far away.
At the top of a mountain cliff, under the dark night sky.
Muzan Kibutsuji stood silently, overlooking the vast land beneath him.
Cold fog surrounded his body. His crimson eyes were slightly narrowed, and a wicked smile appeared on his face.
He looked at the world as though everything belonged to him.
"These humans are strong enough to challenge my demons?"
His smile widened.
"How interesting."
Several enormous tentacles emerged from his back, moving slowly in the darkness.
"That boy... Shinsaku Minamoto. They say he's already killed dozens of my demons. He sounds rather delicious."
He took one step forward.
"Soon, I will meet him."
Then, he jumped from the cliff.
As his body disappeared into the darkness, his thoughts continued.
Unfortunately, Demon Slayers can never become a threat to me.
Not even after centuries.
The night swallowed his figure.
The next day.
Shinsaku stood in his small wooden kitchen, preparing his meal.
His eyes were dull from lack of sleep. Even his usual cheerful expression was nowhere to be seen.
"...I'm overthinking again."
He continued cooking.
But the faces of those who had died kept appearing in his mind.
The families who cursed him. The people who blamed him for failing to save their loved ones. And the burden of always having to be strong.
All of it came back at once.
Yet Shinsaku remained silent.
Moments later, he finished his meal and sat beside the table.
He opened his diary and began writing.
They insulted me again today. They blamed me for their loved ones' deaths, as always.
He paused before writing the next line.
My breathing problem is getting worse. My lungs feel like they're tearing apart.
But I have to keep this a secret from everyone.
He closed the diary and placed it inside a small wooden chest.
A faint smile appeared on his face.
Then, an old memory suddenly crossed his mind—
Years ago.
A young boy was living alone in the hills.
His long hair was messy, his clothes were dirty, and his stomach was completely empty. His lips were dry from thirst.
He had no parents beside him.
No home to return to.
He simply sat there, staring into the distance.
Then, another boy approached him.
He was around the same age, with a rather short stature.
It was Renji.
He looked at the miserable boy with a confused expression.
"Oi... A-Are you living here?"
The young Shinsaku slowly turned his head.
If I hadn't met him that day, I would've died.
———————————————————————
The next morning.
Another old woman grabbed Shinsaku by his collar.
"You son of a bitch! You manipulated my innocent boy!"
Her voice trembled with anger.
"He was only fifteen! If you hadn't come into his life, he would still be alive!"
Shinsaku didn't respond.
His expression remained blank.
He had heard these accusations countless times.
Ohime-san was right… Perhaps I should stop listening to them.
In the afternoon.
The training session had ended.
Shinsaku sat quietly on the wooden veranda, his eyes heavy.
"...I feel like my body is falling apart."
He remembered visiting a doctor a month ago.
The doctor had strictly warned him not to overuse his breathing techniques.
They were still incomplete. And continuing to push his body beyond its limits could have serious consequences.
Shinsaku sighed.
Suddenly—
"Oi, Shinsaku-kun!"
Someone hooked his arms around Shinsaku's neck from behind.
It was Renji.
"You're unusually quiet today. What happened?"
Renji suddenly stopped.
He felt Shinsaku's body.
"Hey... You're burning up!"
Shinsaku stood up.
"I'm not feeling well. I'll take a few days off."
He tried to leave. But Renji's voice stopped him.
"Do you think I don't know what you're hiding?"
Shinsaku froze. His eyes widened slightly.
Renji slowly released his arms.
"I haven't told anyone because you've been keeping it a secret. But at least you could've told me."
He lowered his voice.
"I'm your friend, aren't I?"
Silence.
Shinsaku lowered his head.
"I'm sorry, Renji-kun… I didn't want to become a burden on anyone anymore."
He looked away.
"Please... don't tell anyone."
Renji didn't answer immediately.
Shinsaku quietly walked past him.
Renji remained where he was, watching his back disappear.
For once, he couldn't think of anything to say.
Moments later, Shinsaku reached his small house.
His body was burning. Even breathing had become difficult.
"...I can't breathe properly."
He collapsed onto the bedsheet and closed his eyes.
Just for a few minutes, he thought.
Then everything went black.
Knock. Knock.
Shinsaku slowly opened his eyes.
Someone was knocking.
He forced himself to sit up. His head was heavy, and his entire body ached.
Then he looked outside.
It was already night.
"H-How...!? I thought I had only slept for a few minutes."
"Shinsaku-kun!!"
His eyes widened.
"Renji-kun!?"
He stumbled towards the door and opened it.
Renji stood outside, covered in wounds. His breathing was ragged, and blood ran down his shoulder.
"Shinsaku-kun! Ohime-chan is in danger!"
"...What?"
"We were overwhelmed by the demons. She's still fighting, but she might not survive. Please, you have to help her!"
For a moment, Shinsaku forgot his fever. His expression changed.
"Where is she?"
He grabbed his katana and rushed outside.
Renji followed him. "I tried my best. But we can't win that battle without you."
Shinsaku didn't respond, his eyes sharpened.
Please hold on, Ohime-san.
We won't lose you. Not tonight.
A few moments later.
The battlefield was already a nightmare.
Corpses covered the ground. Blood had soaked into the soil, and the cries of wounded Demon Slayers filled the night.
In the middle of it all stood Ohime.
She was surrounded by demons.
One of her arms had been torn away. Blood covered her face and hair, yet she continued swinging her katana.
She wasn't fighting to protect anyone anymore.
She was simply trying to survive.
"GET AWAY FROM ME!"
She swung her blade.
A demon's head fell, but two more immediately took its place.
Several Demon Slayers tried to protect her, but they were being pushed back.
Then—
"OHIME-SAN!"
Shinsaku and Renji rushed into the battlefield.
They struck down two demons almost simultaneously.
But more appeared.
A demon lunged at Renji. He barely managed to block its claws before another struck him from the side.
"Damn it...!"
He fell to one knee.
Shinsaku tried to move forward, but his legs began to tremble.
His breathing grew uneven.
Not now… Please, not now.
A demon struck him.
He barely avoided it, stumbling backwards before falling to his knees.
His vision blurred.
His chest tightened, and his heartbeat grew unbearably fast. He couldn't breathe.
"Shinsaku-kun!"
Renji tried to reach him, but another demon blocked his path.
All the demons turned towards Shinsaku. He is the only threat to them.
He couldn't move. He couldn't even raise his sword.
So this is it...?
The demons lunged.
Then—
A crimson mark appeared on his forehead.
For an instant, the battlefield seemed to fall silent.
Slash!
Slash!
Slash!
Heads fell before the demons could even touch him.
Their bodies collapsed to the ground.
Everyone froze.
"What... was that?"
"How did he...?"
Shinsaku stood motionless for a moment.
Then his knees gave way.
He collapsed.
The next morning.
Shinsaku slowly opened his eyes.
A wooden ceiling. The faint smell of medicine.
He was lying in a room inside a large mansion, surrounded by bandages and medical supplies.
"W-Where... am I?"
He tried to sit up, but pain immediately stopped him.
"...What happened last night?"
Fragments of the battle returned to his mind.
The demons. Renji. Ohime.
And that strange power.
His hand slowly moved towards his forehead.
"Was that... really me?"
He remembered the crimson mark appearing just before the demons were cut down.
It had happened so quickly that he could barely understand it.
"Something so unnatural… Was it a dream?"
He shook his head.
"No. It wasn't."
He stared at the ceiling.
"...Maybe God still has something planned for me."
Just then, the door opened.
"Shinsaku-kun!"
Renji entered first, followed by Ohime.
Both looked relieved.
Shinsaku's eyes widened.
"Ohime-san..."
He looked at her bandaged shoulder.
"Your arm..."
Ohime glanced down.
"Ah, this? I lost it last night."
She gave an awkward smile.
"But I'm still alive, aren't I? That's what matters."
"That's not something you should say so casually."
Shinsaku lowered his gaze.
"Ohime-san, please listen to me."
He looked directly into her purple eyes.
"You can't fight properly anymore. Your injuries..."
He paused.
"...Please retire from the corps."
Ohime's smile disappeared.
Renji looked towards her.
"I don't think he's wrong, Ohime-chan. We're worried about you. You could live peacefully now. You don't have to keep fighting."
For a while, Ohime said nothing. Then she looked at them.
"I appreciate your concern, really."
Her voice was quiet, but firm.
"But I won't leave."
"...Ohime-san."
Ohime continued. "We made a promise to this Corps. We wanted to make it a better place. We vowed to eradicate demons from this world."
Her eyes didn't waver.
"I won't abandon that promise. Even if I have to die here."
Silence filled the room.
Shinsaku looked down at his bandaged hands.
"I only wanted to keep you safe..."
His voice became softer.
"Because if someone is going to die first…
…It's probably going to be me."
"Stop saying that, Shinsaku-san!"
Ohime immediately interrupted him.
Renji sighed.
"She's right. You're always thinking about things like that. We're still here, aren't we?"
Shinsaku looked at them.
For a moment, he said nothing.
Then a faint smile appeared on his face.
"...You're right."
But he knew.
His body was getting worse. His breathing was failing, and even ordinary days had become difficult. He didn't know how much time remained.
I'm sorry, Renji-kun, Ohime-san. I don't think I'll be here for much longer. But I still have things I must do.
That night.
Shinsaku sat alone on the wooden floor.
Several candles illuminated his small room. His diary lay open before him.
He slowly began writing.
Today, I did nothing but rest.
But something happened last night. Something I still cannot understand.
His hand trembled.
When my heartbeat became extremely fast and my body temperature increased, something awakened within me.
My strength. My speed. Everything changed. I don't know what that power is, or how to control it.
He paused. Then continued.
If someone finds this diary in the future, please remember this.
Perhaps this power will be useful to you.
He closed the diary and placed it inside the wooden chest.
Then he lay down.
"...My body feels heavy."
He stared at the ceiling.
"Even after resting, nothing changes…"
Soon, he fell asleep.
The next morning.
Shinsaku tried to get out of bed. His arms trembled.
"Ugh..."
He struggled to stand.
"What's wrong with my body...?"
It was becoming harder every day.
Just then, the door opened.
"Shinsaku-kun."
He turned his head.
"Renji-kun...?"
Renji looked at him for a moment.
"Come on. We're going to see the doctor."
A little later.
The old doctor examined Shinsaku carefully.
After a while, he turned towards Renji.
"Your friend must stop training. His body is extremely fragile now. He shouldn't even be pushing himself to walk."
Renji looked at Shinsaku.
"Did you hear that?"
Shinsaku lowered his head.
"...I'm sorry."
The doctor frowned.
"Your lungs are swollen. If you continue using those breathing techniques, you won't live much longer."
Shinsaku looked up.
"Then I would rather die."
Renji's expression changed.
"Shinsaku-kun..."
"I have responsibilities. There are people depending on me."
The doctor remained silent.
Shinsaku slowly stood up.
"Thank you for examining me, but I can't stop… Please, try to understand it."
He walked towards the door.
Renji stayed behind for a moment.
"I'm worried about him," he muttered.
The doctor sighed.
"Then make him understand that his life matters too."
Renji didn't answer.
Several days passed.
Shinsaku's condition continued to deteriorate.
He could barely sleep. His body remained weak, and even simple tasks exhausted him.
Yet he continued searching.
Late at night.
Torn pages and old manuscripts covered the floor.
Shinsaku sat in the middle of them, his eyes bloodshot.
"Damn it...!"
He clenched his head.
"Why can't I find anything!?"
His voice echoed through the empty room.
"I've searched every book I could find. Every record. Every old manuscript!"
He struck the wooden floor with his fist.
"I found nothing!"
His breathing became uneven.
For a while, he simply sat there. Then, he slowly lowered his head.
"...I'm losing my mind."
He took several breaths, trying to calm himself.
So many people are dying… And what am I doing?
I'm sitting here, reading old pages, waiting for an answer that might not even exist.
His eyes moved towards the scattered manuscripts.
"I told them not to follow me. I took their responsibilities. I promised myself that I would protect them."
His voice became quieter.
"...But I can't even protect myself."
He stared at his trembling hands.
What am I supposed to do?
How many more people must die before I find a way?
Tap. Tap.
Something struck the window.
Shinsaku slowly turned.
A black crow stood outside.
"...A crow?"
CAW! CAW! CAW!
His expression changed.
He understood its message.
"Wait... What?"
He immediately stood up.
"Is that really true?"
He grabbed his katana and rushed towards the door.
He barely remembered to close it.
This has never happened before…. Why tonight?
He ran into the darkness.
Somewhere else.
In a library,
A red lamp illuminated the shelves, casting long shadows across the walls.
A man sat in a chair, his legs crossed.
Muzan Kibutsuji.
He closed the book in his hand.
"Years have passed... and still, no trace of the Blue Spider Lily."
He placed the book on the table.
A faint smile appeared on his face.
"I once wanted to meet that man, Shinsaku Minamoto."
His crimson eyes narrowed.
"But a mere human is hardly worth my time."
He leaned back.
"Still..."
His smile widened.
"I've already made arrangements."
For a moment, the room became silent.
Then Muzan spoke.
"Tonight, Shinsaku Minamoto will die."