Isekai Adventure in the Dimensional Cube

"————"

Consciousness began to return.

With the dissolution of the dream, Reiger could clearly feel himself coming back to reality, back to sitting on the train.

It was as if he had been dozing off, his body gently rocking with the movement of the train, the sound of the whistle echoing more and more clearly in his ears. All his senses became real again, unlike just moments ago in the dream where even the wind and the sunlight hitting his skin carried no sensation.

But it was precisely because of this return to sensation that Reiger was astonished to discover that his surroundings had massively transformed.

"Bang!"

A tentacle-like appendage, resembling a column of flesh, swung past in front of Reiger, striking an unoccupied seat and smashing it to pieces.

The wooden carriage, which had seemed somewhat desolate, now resembled the interior of a body's intestine, with walls of flesh on all sides and numerous tentacles, like columns of meat, crazily writhing about.

"What is this?"

Reiger looked on with a trace of astonishment at the scene.

"Yo! You're finally awake, Lunchbox Boy!"

As Reiger felt bewildered, a familiar, hearty voice reached his ears.

Rengoku Kyoujurou, wielding a katana with a black base and red blade, was fighting tentacles coming from all directions while standing back to Reiger.

"Breath—hold—"

Rengoku Kyoujurou assumed the iaijutsu stance, lowering his body and inhaling a large amount of oxygen. While exhaling, he murmured softly.

"Flame Breathing Fourth Form· Intense Flame's Winding."

Flames erupted from Rengoku Kyoujurou's katana as he swung it like a windmill, cutting rapidly all around.

Instantly, a vortex of fire appeared in the flesh-wall and tentacle-filled carriage. As Rengoku Kyoujurou struck, it blasted towards the surroundings.

"Pfft!"

All the attacking tentacles were severed into pieces of flesh the moment they touched the fiery vortex as if they were cut by high heat.

Rengoku Kyoujurou thus continued to sever the incoming tentacles with his fiercely burning sword technique.

"Swoosh!"

"Swoosh!"

However, the tentacles on the train seemed endless; as soon as one was cut down, new ones grew out from the flesh walls, assaulting Rengoku Kyoujurou en masse.

Rengoku Kyoujurou was just about to turn and counter when a streak of silver light flashed by at an extreme speed.

"Pfft—"

The silver light merely grazed the tentacles, and they were instantly shredded as if by a grinder, cut into numerous pieces in a moment.

Reiger, with a bright silver short sword in hand, appeared behind Rengoku Kyoujurou as if he had teleported, moving so fast that even Rengoku Kyoujurou couldn't react in time.

Rengoku Kyoujurou's pupils shrank, followed by a wide smile spreading across his face.

"Hmm, just as Inosuke, the teary boy, and the boar-headed boy said, you're strong, Lunchbox Boy!"

With that, Rengoku Kyoujurou entrusted his back to Reiger, turning his flame blade and cleanly severing the attacking tentacles in front of him.

Reiger made it look even easier than Rengoku Kyoujurou, standing still and casually swinging his sword-hand. Any tentacle that reached him was swiftly sliced into many pieces by the flashing silver light, cut beyond possibility of regrowth.

"What's the situation now?"

Reiger found a moment to ask Rengoku Kyoujurou behind him.

"Hmm! It's a dire situation!" Rengoku Kyoujurou responded directly, "In short, it seems we've been targeted by a demon lurking on the Infinite Train from the moment we boarded. When the conductor was checking tickets, we all fell into that demon's Blood Demon Art and entered a dream. If it hadn't been for the scarred boy breaking free from the dream, things could have been troublesome!"

The 'scarred boy' referred to Kamado Tanjirou.

While everyone was trapped in dreams, Tanjirou was the first to figure a way out, returning to reality and awakening the others.

The reason everybody had been hypnotized remotely was all due to that ticket mixed with demon blood.

Tanjirou managed to burn the ticket, which allowed everyone to fully awaken. Only Reiger hadn't woken up yet because he was not completely under the demon's hypnotic effect when he entered the dream, creating the situation where Rengoku Kyoujurou had to fight while protecting him.

This development was almost no different from the original plot.

In the original story, it was Tanjirou who first broke free from the dream and then helped everyone escape the hypnotic state, allowing them to wake up.

However, as Reiger had previously thought, the hidden demon did not merely tamper with the ticket; the entire train had been rigged by the adversary.

The reason the train had turned into a mass of flesh walls with tentacles everywhere was that the demon on the Infinite Train had actually merged with the train, turning it into its own body.

In other words, the place Reiger and others were in was not the actual Infinite Train, but the interior of a demon that took the shape of the Infinite Train.

"It seems the demon plans to devour all two hundred passengers on the train at once, so the boys have started acting separately. Some are searching for the demon to carry out a beheading mission while others are protecting passengers in other carriages!"

Rengoku Kyoujurou pressed down, his entire being surging forward like a pillar of fire, charging forward and severing countless tentacles, even cutting through several other carriages.

In those carriages, tentacles originally aimed at the slumbering passengers were all sliced into pieces and exploded under the swift charge and slash of Rengoku Kyoujurou.

Rengoku Kyoujurou then charged and slashed through several carriages continuously, and in the blink of an eye, he was back, surging like a pillar of fire, with a speed that was astonishing.

"That's the situation! It's still quite grim!"

Though he spoke casually, the smile on Rengoku Kyoujurou's face never faded, not only dispelling any sense of tension but also conveying a sense of effortless control.

In response, Reiger also smiled faintly. In a flash, he transformed into a whirlwind, instantly charging through several carriages.

"Pfft— Pfft— Pfft—"

Wherever the whirlwind passed, the sword light burst out like a storm, severing the tentacles reaching for the passengers and slicing them to pieces.

Soon, Reiger returned to his original position. Along the way, not only the tentacles but also the flesh walls were slashed into a bloody mess by the gleaming sword strikes, struggling to regenerate.

"Whoa!"

Rengoku Kyoujurou's eyes changed once again.

The strength Reiger demonstrated greatly exceeded Rengoku Kyoujurou's expectations.

Such might, within the Demon Slayer Corps, could certainly rank among the Pillars.

No, even among the Pillars, Reiger seemed to slightly surpass them at this moment.

"Didn't I tell you?" Reiger didn't pay heed to the surprise he had caused Rengoku Kyoujurou and said, "Fighting against strong demons while protecting two hundred passengers, even you would find it tough."

"Yes! It is beyond my current ability!" Rengoku Kyoujurou nodded in acknowledgment and declared loudly, "But no matter! I will still protect everyone here! I won't let anyone die!"

The flames around Rengoku Kyoujurou burned even more fiercely.

But as he prepared to fight with all his might, stoking the flames in his soul and body, Reiger spoke calmly.

"There's no need." Reiger bluntly said, "We're inside the demon's body. As long as we stay on this train, we'll continuously have to battle the demon, and the passengers will be under constant threat. Instead of defending passively, it would be better to find a way to transfer all the passengers out of here."

Perhaps understanding what Reiger said, the flesh walls around them writhed, and immediately numerous tentacles sprouted out, attacking him.

"Pfft!"

A flash of silver light suddenly cut off all the tentacles, causing them to fall to the ground.

"Boom!"

Rengoku Kyoujurou also transformed into a column of fire once again, rapidly charging back and forth through several carriages, cutting off each tentacle before returning to Reiger's side.

"The train is moving at top speed. How can we transfer two hundred passengers out of here?"

Rengoku Kyoujurou's katana blazed with an intense fire, making the temperature inside the carriage rise continuously.

"Then let's first bring the train to a halt," Reiger said as he unleashed numerous sword lights, severing tentacles and flesh walls while speaking to Rengoku Kyoujurou, "Once I get the train to stop or even dissect it, you will transfer all the passengers out safely at the fastest speed possible, okay?"

"Oh? You have a way to stop the Infinite Train?" Rengoku Kyoujurou paused for a moment, then without thinking further, he immediately promised, "No problem, I'll get all the passengers out the moment the train stops."

"Good." After slicing off a few more tentacles, Reiger turned his head to look at Rengoku Kyoujurou and said, "Be careful."

"Yeah!" Rengoku Kyoujurou grinned and without looking back, responded, "You too!"

Reiger smiled noncommittally and disappeared from the spot with a flicker.

Feeling the presence behind him vanish, Rengoku Kyoujurou's smile grew even wider.

"This journey is fantastic—to have met such an excellent companion, I, Rengoku Kyoujurou, am truly honored!"

Rengoku Kyoujurou was very pleased.

Meanwhile, he felt a bit puzzled.

"However, I can't help feeling that Bento Boy's breathing has changed. It feels incredible, like an illusion?"

While Rengoku Kyoujurou was pondering this, the tentacles attacked once again.

"Hmm! Better complete the mission first before I dwell on it!"

Rengoku Kyoujurou concentrated, stopped all wandering thoughts, and with flames wrapping around him, he dashed towards other carriages.

...

"Woo—"

In the desolate wilderness, on the railway track, a train sped through the night, emitting bursts of steam whistles and wheel sounds.

Only this train was now covered in flesh walls everywhere, which looked somewhat grotesque and nauseating.

"Inosuke! Hurry up!"

At that moment, Tanjirou was running on the roof of the train, shouting to the boar-headed companion beside him while running.

"I know! Watch me! Beast Breathing, Rushing Boar!"

Inosuke, holding two serrated blades, charged wildly headlong towards the front of the train.

"Bang!"

Just then, a figure shattered the train's wall and leaped over the heads of the two.

"Eh?"

Tanjirou looked up in surprise.

"Big, Big Brother?"