Scene: Meeting at Obayashiki Headquarters Before the Mugen Train Mission

All the Hashira stood quietly in the courtyard of Obayashiki Headquarters, with Tanjiro, Zenitsu, Inosuke, Nezuko (inside her box), and Kanao standing beside them. Moments later, Kagaya Obayashiki arrived with his wife, and a hush fell over the room in respect.

Kagaya:

"Thank you all for coming. I summoned you today because of a matter that has become more serious than we anticipated."

Everyone turned their attention to him.

Kagaya:

"Over the past few weeks, more than forty passengers have disappeared on the Mugen Train. Not one of them survived."

Silence fell over the room.

Rengoku:

"More than forty people... this is not something to ignore."

Gyo:

"Have you confirmed that a demon is responsible?"

Kagaya:

"Yes. We also sent several demon slayers to investigate, but they also disappeared, and none of them returned."

Shinobu:

"So we're facing an intelligent demon... not just any ordinary one."

Obanai:

"Have we found out his identity or rank?"

Kagaya shook his head.

Kagaya:

"Unfortunately, no. The crows haven't been able to identify him yet. We only know that all the incidents are connected to the Mugen train."

Sanemi:

"Then there's no need to waste time. Let's go and kill him."

Tengen:

"If he's such a mysterious demon, then this sounds intriguing."

Moichiro:

"We don't have enough information... we have to be careful."

Mitsuri:

"I hope the passengers still on the train are safe..."

Jiyomi:

"May God have mercy on the victims... and may God prevent any more from falling."

Kagaya glanced at Rengoku.

Kagaya:

"Rengoku... I'm assigning you to lead this mission."

Rengoku smiled confidently.

Rengoku:

"With pleasure! I will protect all the passengers, no matter what!"

Kagaya then looked at Tanjiro and his companions.

Kagaya:

"Tanjiro... Zenitsu... Inosuke... you will join Rengoku on this mission."

Tanjiro:

"Yes, sir!"

Zenitsu:

"A... train?! I have a very bad feeling..."

Inosuke:

"Haha! Finally, a big mission! I will defeat the demon myself!"

Kagaya smiled calmly.

Kagaya:

"Move immediately to Mugen Train Station and begin the investigation. We don't know what kind of power the demon possesses, so don't underestimate him."

Everyone bowed respectfully.

Everyone:

"Yes!"

And with that, the meeting ended, and Rengoku left with Tanjiro, Zenitsu, and Inosuke, heading towards Mugen train station, none of them knowing that the demon waiting for them was Enmu, the first lower-ranking, and that this mission would lead them to one of their toughest battles.

Scene: After the Obayashiki Headquarters Meeting

After the meeting concluded, everyone bowed respectfully to Kagaya. Then, Rengoku, accompanied by Tanjiro, Zenitsu, Inosuke, and Nezuko, left inside her box, heading towards the nearest station.

---

Inosuke:

"Hahaha! Finally, a big mission! I'll be the first to defeat that demon!"

Zenitsu:

"Shut up! I don't even want to take the train! I have a bad feeling..."

Tanjiro:

"Relax, Zenitsu, we'll be together."

Rengoku walked confidently, looking straight ahead.

---

Mugen Train Station

The station was crowded with passengers waiting for their train to depart.

Inosuke gazed eagerly at the train.

Inosuke:

"What an iron beast! I'll defeat it before the demon!"

Then, he lunged towards the train and headbutted it.

Bang!!

He fell to the ground in pain.

Zenitsu:

"You're stupid!! It's just a train!"

Tanjiro chuckled softly, while Rengoku simply looked at them.

---

Inside the train

Everyone boarded the train and took their seats.

As soon as the food reached Rengoku, he started eating very quickly.

Rengoku:

"Delicious!"

Then he took another bite.

Rengoku:

"Delicious!"

He kept repeating it with every bite.

The three of them looked at him in amazement.

Inosuke:

"How big is his stomach?!"

Zenitsu:

"Is he going to stop eating?"

Tanjiro just smiled.

---

A little while later...

Rengoku explained why he was there.

Rengoku:

"More than forty people have disappeared on this train, and several Demon Slayers sent to investigate have also disappeared."

Tanjiro:

"So the demon is really here."

Rengoku:

"Yes... but we don't know where he is or what kind of ability he has."

---

Enmu Appears

The ticket clerk was walking among the passengers.

After checking the tickets, a strange man sat quietly inside one of the carriages.

He smiled a terrifying smile.

That was Enmu... the lowest rank.

In his mind, he said:

"Grow up... and enter your sweet dreams."

He used his Blood Art.

And suddenly...

Rengoku, Tanjiro, Zenitsu, Inosuke, and even all the passengers fell asleep.

---

Dreams

Tanjiro

He found himself inside his old house.

He saw his mother and all his siblings alive.

He ran towards them, crying with joy.

---

Rengoku

He returned home.

He remembered his mother, who always encouraged him to protect the weak.

---

Zenitsu

He found himself walking with Nezuko, who was holding his hand.

He began to shout with joy.

---

Inosuke

He imagined himself as the great leader of the adventure.

And Tanjiro, Zenitsu, and Nezuko were his followers.

---

At the same time...

Enmu hired several people for money.

He ordered them to enter the dreams of the Demon Slayers and destroy their soul cores so they would never wake up.

---

Tanjiro wakes up

Inside his dream, he began to feel something strange.

He remembered the mission.

He remembered Nezuko.

Then he realized that everything he was seeing was just a dream.

But he didn't know how to wake up.

Until he heard a voice telling him that death within the dream would awaken him.

He raised his sword...

And cut off his head within the dream.

---

He suddenly opened his eyes inside the train.

He found everyone still asleep.

At that moment, Enmu appeared before him.

He smiled and said,

"You're the first to wake up... but you can't wake the others."

Tanjiro began attacking him, but Enmu kept sending him back to sleep.

Each time, Tanjiro would cut off his head in the dream and wake up again.

---

Enmu's Fusion with the Train

After realizing he couldn't defeat them in the usual way...

He used his most powerful technique.

His body began to melt...

Then he completely merged with Mugen's train.

All the carriages became part of his body.

His flesh and arms spread throughout the train, devouring more than two hundred passengers at once.

---

Dividing the Tasks

Rengoku:

"I'll protect the passengers!"

He sped through the carriages at incredible speed.

He severed all the arms that attacked the passengers, ensuring no one died.

Meanwhile...

- Tanjiro and Inosuke headed towards the front of the train to search for Enmu's neck.

- Zenitsu stayed behind to protect Nezuko and the passengers.

- Nezuko used her blood to burn Enmu's flesh and protect the people.

---

The End

After a long fight...

Tanjiro and Inosuke reached Enmu's neck.

With a combined blow...

They severed his head.

His body began to gradually disappear.

The train finally came to a stop.

Everyone sat catching their breath, thinking the mission was over...

But suddenly...

Rengoku felt a terrifying force rapidly approaching.

A figure landed in front of them, smashing the ground with force.

It raised its head with a calm smile and said,

"Good evening..."

It was...

Akaza... the third-ranked Supreme.

A heavy silence fell after the strange demon appeared.

Dust swirled from the shattered ground as everyone stood staring in shock.

His eyes held the number "Third Supreme Rank."

Tanjiro froze.

Tanjiro:

"...Supreme Rank?!"

The demon smiled calmly, looking directly at Rengoku.

Akaza:

"Finally... I've found someone powerful."

He took a step forward without looking at anyone but Rengoku.

Akaza:

"You're the Flame Hashira...aren't you?"

Rengoku replied steadily.

Rengoku:

"That's right."

Akaza smiled.

Akaza:

"Your name is Kyojuro Rengoku...I can see from your spirit that you've become powerful after years of training."

Rengoku gripped his sword hilt.

Rengoku:

"Who are you?"

Akaza:

"I am Akaza... the third highest rank."

Tanjiro's eyes widened.

Zenitsu and Inosuke felt an immense pressure emanating from his body.

Akaza raised his hand, smiling.

Akaza:

"Transform into a demon, Rengoku."

Silence fell.

Akaza:

"Humans age... but we remain strong forever. You will be able to reach much higher levels."

Rengoku glared at him.

Rengoku:

"I refuse."

Akaza smiled as if he had expected it.

Akaza:

"Poor thing..."

Then his smile vanished.

In a split second...

He disappeared.

Boom!!

He shot forward with incredible speed toward Rengoku, landing a direct punch to his head.

But Rengoku drew his sword at the same instant.

Clash!!

The fist collided with the sword, and the ground shook beneath their feet from the sheer force.

Both leaped backward.

Rengoku drew his sword.

Rengoku: "Breathe the flames...!"

Akaza assumed his fighting stance, smiling confidently.

Akaza: "Show me... the power of the Hashira."

And so began the decisive battle between the Flame Hashira Kyogoro Rengoku and the third-ranked Akaza, while Tanjiro, Zenitsu, and Inosuke watched the fight, unable to intervene due to the overwhelming disparity in strength.