1000 years ago.
Heian Era.
Before the Upper Moons came into existence. Before the Kakushi became part of the Demon Slayer Corps. Before even the Breathing Styles were invented.
It was a terrible night.
The village was surrounded by darkness. Screams echoed through its narrow streets as demons dragged away helpless humans and devoured them.
A small group of Demon Slayers had arrived to stop the massacre. But they were already losing.
There were six demons, and only three Demon Slayers standing against them. Their opponents were not only stronger, but also faster. Every time the Slayers managed to land a strike, the demons quickly recovered and attacked again.
One of the Demon Slayers stumbled backwards, clutching his bleeding shoulder.
"Demons are too powerful! There's no way we can defeat them in a fair fight!"
"Besides, we're outnumbered! We must leave immediately!"
Before he could take another step, a demon lunged towards him. Its claws came straight for his face, only a few inches away from his eyes.
Slash!
A woman's katana cut through the demon's neck. Its head rolled across the ground.
"What are you doing!? We don't have time to stand around talking!"
Her breathing was ragged. Blood trickled down her forehead, but her amethyst-purple eyes remained sharp.
Without waiting for a response, she rushed towards another demon. She swung her katana at its neck, forcing it to retreat. However, two other demons suddenly attacked her from either side.
"What—"
She couldn't turn around in time.
Both demons struck her at once, sending her crashing into the ground. Her katana slipped from her hand, and blood began running down her wounded arm.
Before she could get back up, one of the demons crawled over her, opening its mouth.
"Finally...!"
Slash!
Its head was severed before it could bite her.
A tall young man stood between the woman and the demon's body. His long hair was tied into a ponytail, and his katana was still raised.
Shinsaku Minamoto.
He turned towards the woman and extended his hand with a cheerful smile.
"Get up, Ohime-san. You can't rest here."
Ohime clenched her fist and glared at him.
"You dumbass! Do you think I'm resting here!?"
She grabbed his hand and stood up. But the moment she looked behind him, her expression changed.
"Shinsaku-kun! The demons are behind you! Be careful!"
The remaining four demons had already leapt into the air. Their claws were spread wide, and all four were aiming directly at him.
Shinsaku didn't turn around. He simply took a deep breath.
His chest expanded, and the muscles throughout his body tightened. His grip on the katana became firm.
Then—
Slash!
Slash!
Slash!
Slash!
Four consecutive strikes cut through the darkness.
The demons' heads separated from their bodies before they could even reach him. Their corpses fell to the ground, slowly turning into ashes.
Silence returned to the street.
Shinsaku lowered his katana and calmly returned it to its sheath.
The other two Demon Slayers stared at him in disbelief.
"W-Wow, Shinsaku-kun... You killed all of them so effortlessly."
Shinsaku didn't respond immediately. He brought his hands together in prayer and slightly lowered his head.
"May you all rest in peace."
His expression was gentle, but his eyes carried a certain sadness.
The night was finally over.
The next morning.
The sky was clear, and sunlight slowly spread across the village.
But there was no relief in their faces. Several old men and women had surrounded Shinsaku. Their eyes were swollen from crying, and their voices were filled with anger.
"You people killed our son too!"
"How many more lives must we lose because of your organization!?"
An old woman suddenly stepped forward and grabbed Shinsaku by the collar.
"You son of a bitch! You promised to protect my daughter! She was supposed to get married in two days! Two days!"
Her hands trembled as she pulled him closer.
"But now she's dead! She's dead because of you people!"
Shinsaku remained silent.
Ohime and the other two Demon Slayers stood nearby. They wanted to intervene, but none of them could bring themselves to stop the villagers.
Ohime lowered her gaze and turned her face away. Her wounded arm was wrapped in bandages, but the pain in her chest was much harder to ignore.
Moments later.
Ohime and Shinsaku sat on the veranda of the wooden house. Ohime had tied her hair into a bun and changed into her purple haori.
She looked at Shinsaku.
"Shinsaku-kun, why do you always listen to those people? You did nothing wrong. They lost their family members, but you can't carry their anger every day."
Shinsaku smiled quietly.
"I'm not angry at them. I just feel sad. If I were in their place... I might do the same."
Ohime frowned.
"But how long are you going to keep taking their burdens on your shoulders? One day, it will break you."
Shinsaku became silent. Then he said, "I know."
He looked toward the village.
"But they joined us because they believed in us. So... it's our duty to save them."
"You're not understanding what I mean..."
Before Ohime could continue, someone called from behind them.
"Oi, Shinsaku-kun."
A young man walked toward them. He was around 5'3 and had a rather ordinary appearance. He tied his hair into a long ponytail.
"Renji-kun," Shinsaku said.
Renji looked at Ohime.
"Ohime-chan, you too. Oyakata-sama ordered both of you to come."
Shinsaku blinked. "What's the matter?"
Renji stared at him.
"If I knew, wouldn't I tell you right away?"
Shinsaku's hand clenched slightly.
"I see... But you could have just said that."
Renji sighed. "You're too sensitive."
Ohime covered her mouth, trying not to laugh.
Shinsaku forced a smile.
"Let's go."
Some moments later.
The three arrived at the Ubuyashiki mansion. They sat on the floor in front of the Corps leader. The man was in his forties.
He was the first Oyakata-sama of the Demon Slayer Corps. His voice was strangely metallic.
"Shinsaku. Ohime. Renji."
The three looked at him.
"I have important work for you."
Shinsaku smiled softly.
"What work, Oyakata-sama?"
"I want the three of you to train the other Demon Slayers. You are stronger than most of them… Killing a demon alone is still extremely difficult."
He looked at Ohime.
"Ohime, you will train the female candidates."
Ohime nodded.
"Yes, Oyakata-sama."
Renji raised his hand.
"I understand. But how much will we earn?"
Silence.
Shinsaku and Ohime slowly turned toward him. Renji looked back.
"What?"
Oyakata-sama's expression twitched.
"You're asking about money before saving lives?"
Shinsaku immediately covered his face.
Oyakata-sama sighed.
"Renji... You are too immature. You will receive extra pay at the end of the month. Now do your work properly."
Renji nodded. "Understood."
Shinsaku looked at him.
"You're unbelievable."
"What? Money is important."
Ohime sighed. "Please stop talking."
The room became quiet again.
Shinsaku then raised his head.
"Oyakata-sama, may I ask something?"
"Go ahead."
"When we finally encounter Muzan Kibutsuji... how will we know it's him?"
Oyakata-sama's expression changed slightly.
Shinsaku continued.
"You said he is related to your bloodline. So... you might have seen him before."
Silence.
For a moment, nobody spoke. Then Oyakata-sama said,
"When you encounter him, your instincts will tell you."
Oyakata-sama lowered his voice.
"But if you want details, listen carefully."
He looked directly at Shinsaku.
"Muzan has crimson pupils and cat-like eyes. Pale skin. Medium height. His face is ruthless, and his presence is cold."
Shinsaku quietly listened.
"That is all I know. It has been many years since I saw him."
He lowered his gaze.
"He is my distant cousin."
Ohime's eyes widened slightly.
"When he became a demon, our bloodline was cursed."
Shinsaku asked, "What kind of curse?"
"No man in our family lives beyond thirty."
Renji suddenly spoke.
"But you're forty."
Shinsaku's eyes widened. Shinsaku grabbed Renji's face and covered his mouth. "Shut up."
Ohime looked away in embarrassment.
"I'm sorry, Oyakata-sama. Renji-kun is... sometimes immature."
Oyakata-sama stared at Renji.
"Renji."
Renji pulled Shinsaku's hand away.
"Yes?"
"You will receive your extra pay only if you complete your work efficiently."
Renji became serious. "Understood."
Some moments later.
The three left the mansion. Renji stretched his arms.
"That old fart thinks he owns us. I still wonder how he's even alive."
Ohime immediately looked around.
"Be careful! Don't say things like that in public."
"Whatever."
Shinsaku looked at the two of them and sighed.
Then the three reached a fork in the road.
Ohime went left. Renji went right. Shinsaku continued straight.
They separated without another word.
The next day.
Different people gathered around Shinsaku again.
This time, Ohime was with him. Their voices were filled with anger and grief.
"You terrible monsters killed my son!"
"You promised to save them!"
"You said they would come back!"
Shinsaku and Ohime said nothing. They simply listened.
Hours later.
It was afternoon.
Shinsaku had finished his training. He was sweating, but his breathing was still calm.
Around him, the other Demon Slayers were exhausted, gasping for breath. One of them looked at him in disbelief.
"Shinsaku-san, you're too strong. You're not even tired. How did you become this strong?"
Shinsaku smiled.
"I learned how to control my breathing. Concentrate on your breathing, and you can control your body better."
"But this doesn't work that much," another Demon Slayer said. "How can someone become this strong just by controlling their breathing?"
"I can make my body pump harder. It should work for everyone. If it doesn't, you need more practice."
He smiled again.
"Just train harder."
The third Demon Slayer stared at him. "You became this strong just by controlling your breathing? It sounds unbelievable."
Shinsaku laughed.
"Anyone can do it. Keep training and practicing your breathing techniques. Eventually, you'll become strong."
The training session ended. Everyone left.
Shinsaku also returned home.
The moment he entered his small wooden house, he closed the door and leaned against it.
His smile disappeared. His chest tightened. His entire body began to tremble.
"H-How..."
He covered his mouth as his vision became blurry.
"My body is becoming more numb... I'm overusing my breathing capacity."
His knees nearly gave out. For a moment, everything went dark.
Then he gasped and regained consciousness.
"But this is the only way to become stronger."
He slowly stood up.
"To fight demons... to save others."
He looked at his trembling hand.
"But... I don't think I'll live long if this continues."
Knock.
Shinsaku froze.
Knock. Knock.
"Oi, Shinsaku. Are you not listening?"
He recognized the voice.
It was Renji.
Shinsaku quickly forced his usual smile onto his face and opened the door.
Renji stood outside.
"I've been knocking for two minutes. What were you doing?"
"I'm sorry. I didn't notice you."
Renji entered without asking. He looked around the house.
There was little furniture. The wooden walls were plain, and the room was barely decorated.
Then Renji noticed the bookshelf. He walked toward it and looked through the books.
Old fantasy books. Mythical stories. Traditional writings.
He picked one up and laughed.
"Shinsaku-kun, you really love these kinds of books."
Shinsaku tried to take it from him. "Stop it."
Renji dodged him.
"That's why you always act like some kind of protagonist."
Shinsaku finally took the book back and placed it on the shelf.
Renji sighed.
"You always live in a fantasy. The protagonists in these books are exaggerated. Do you really think a calm, serene and extremely powerful protagonist can exist in real life?"
"I don't."
Shinsaku smiled.
"But you're taking it too personally, Renji-kun."
Renji ignored him. His eyes moved toward another drawing.
He stopped.
"A demon emperor?"
He picked up the paper.
A tall human stood in the center. Pale skin. Long black hair. Crimson eyes. Black clothes. Blood surrounded him.
Renji's expression changed. Then he noticed another drawing beside it. The name written on the page was:
Muzan Kibutsuji.
The drawing showed a terrifying humanoid demon with multiple eyes, long hair, a muscular body and a long demonic sword.
Renji stared at it.
"These drawings are completely different from what that old geezer described."
Shinsaku became slightly embarrassed.
"These... were just my interpretation of how Muzan might look."
"You were wrong."
"I know."
Renji looked at Shinsaku again. For a moment, his expression became serious.
"You seem tired."
Shinsaku said nothing.
"Maybe today's training was too much."
Renji walked toward the door.
"I'll come back later. Don't overload yourself."
He left.
The door closed. Silence filled the house.
Shinsaku's smile slowly disappeared.
He sat on the floor. Beside him was a small wooden chest.
He opened it. Inside were several bottles of medicine.
He stared at them for a long time.
"...I'm sorry, Renji-kun."
His fingers tightened around one of the bottles.
"I can't tell you about this."
He lowered his head. Then his eyes moved toward the drawings.
"...I don't think we can ever defeat Muzan Kibutsuji…
…Not even after centuries."