Isekai Adventure in the Dimensional Cube

The Brillhaut residence, Reiger's room.

After leaving the sitting room, Reiger went straight back to this temporary room of his and locked the door from the inside.

Just a moment ago, he had informed Yuri that he was going to rest in his room for the day, asking not to be brought food or disturbed, with all matters to be discussed tomorrow.

Yuri readily agreed and instructed Reiger to rest well and recover from his injuries, telling him that other issues could wait until he was truly better.

Indeed, Yuri believed Reiger's injuries from yesterday had not yet fully healed, which is why she didn't question why he made such a request.

But Reiger had already fully recovered from his injuries and naturally wasn't returning to his room to rest and recuperate.

Having decided to undergo Dimensional Travel again and pursue the goal of becoming a Sword Saint, Reiger did not wish to delay any further.

With Yuri's engagement already resolved and the royal capital taken care of, even the War Festival was over; in the short term, there shouldn't be any other important matters to deal with.

"Even if there are other matters, they can't be so urgent as to not afford me a single day, right?"

No matter how much time passes in other worlds, only one day will have gone by on the continent of Akasha.

In the span of just one day, Reiger couldn't believe anything significant would happen.

However, considering safety issues, Reiger decided to take some precautionary measures.

"O Wood Spirit—fulfill my wish."

"O Garment of the Forest—my name is Alf."

"Thin Veil Breath."

Reiger cast a magic spell.

Instantly, a green vestment-like membrane of light enveloped him.

This was one of the three defensive spells Revilia had taught Reiger, the Garment of the Forest, capable of withstanding any attack from the enemy.

Of the three defensive spells Revilia had taught, this one ranked second, with exceptional protective capability, far more reliable than the "Endurance" enhancement granted by Lamu.

Reiger poured most of his spiritual power into this spell, and as long as he wasn't attacked frequently, it should last a long time, persisting until Reiger's return.

During his last Dimensional Travel, Reiger had no means to protect his original body left in his world while his consciousness traveled to another, and at that time, he was too eager to gain the power to protect himself to consider much else and hastily underwent Dimensional Travel to the Earth Mistake World.

But this time, Reiger already possessed sufficient power to protect himself, so naturally, he couldn't leave his physical body in the original world unprotected while undergoing Dimensional Travel.

If it weren't for the fact that he was in the Brillhaut residence, Reiger would have even considered using his strongest Barrier Magic.

Unfortunately, that spell was a Barrier Magic that would surely encompass the surrounding area if cast, potentially causing a significant disturbance.

Thus, Reiger had to abandon that idea, instead using Thin Veil Breath for protection.

Having completed these preparations, Reiger set up some minor spells on the door lock and other areas, which would inform him upon waking whether anyone had unlocked the door or entered the room.

These minor spells were taught to him by Yuri.

And they just might come in handy now.

"Before Dimensional Travel, let's update my ability values first."

Reiger took out Divine Blood from Loki, dripped it on his forehead, and as his back shone with a pale glow, Holy Text began to flutter about.

Before long, Reiger's latest ability values were freshly updated.

...

Reiger Brillhaut

Lv.5

Strength: G284 → D570

Endurance: G257 → D555

Dexterity: F312 → C611

Agility: F331 → C637

Magic Power: F305 → C632

Light Armor: G → F

Swordsman: G → F

Spellcasting: H → G

Good Fighter: I

...

The last ability update was back when he was in the royal capital.

Since leaving the capital, Reiger first took a daylong carriage ride to Trentia, then spent three days on a ship to the Brillhaut territory, and a week preparing before the War Festival; all in all, it's been about two weeks since the last ability update.

In less than two weeks, the total proficiency of his abilities had increased by over 1500, which was quite commendable in a world without dungeons or monsters to defeat.

Of course, the most surprising was the upgrade of all three development abilities by one rank.

"That makes sense; I've been practicing sword skills and magic non-stop, so it's only natural that the 'Swordsman' and 'Spellcasting' development abilities should have grown."

'Light Armor' seems to have improved in rank due to Reiger not wearing heavy burdens in battle or training.

'Good Fighter' saw no improvement, which was unsurprising given that it was closely related to battle, and since returning to this world, Reiger had only experienced a few fights.

Overall, Reiger was quite satisfied with this growth.

With this, he would be able to engage in the upcoming Dimensional Travel in the best state.

Thinking of this, Reiger sank his consciousness into his mind, into the slowly rotating transparent cube in his mind.

Reiger first checked the amount of Dimension Energy he had left.

"Dimension Energy: 40"

When Reiger returned to this world, his remaining Dimension Energy was 23 units. Now, about half a month had passed, and it had accumulated to 40 units.

A random Dimensional Travel requires 30 units of Dimension Energy, and Reiger had enough remaining.

So—

"Dimensional cube, activate the dimensional passage."

Reiger instructed the transparent cube in his mind.

Then, just like the first time Reiger undertook Dimensional Travel, the transparent cube in his mind began to rotate.

"Command accepted, initiating activation of the dimensional passage."

"Energy sufficient, dimensional passage construction beginning."

"Construction successful."

The transparent cube rotated, its individual cubes detaching from the main body, decomposing into countless transparent cubes which rotated and interlocked with each other, eventually forming a channel that connected to the end of the sea of consciousness and disappeared into the void.

"Dimensional passage opening complete, intelligence gathering finished."

"Information highly compatible with the world on the other side of the passage has been searched from the user's memory and is now being organized."

"Organization successful."

"Connected world: Demon Slayer."

"Time ratio: 1:180."

"This Dimensional Travel will materialize the user's consciousness. The consciousness will gain a physical form. Death of the materialized consciousness will not affect the user, but it will also signify the end of this Dimensional Travel. Please proceed with caution."

The instant the Dimensional Travel construction succeeded, the dimensional cube also relayed the information about this Dimensional Travel to Reiger's mind, which he received.

Suddenly, Reiger was stunned.

"Demon Slayer?"

Is it really that world?

Reiger's memory was immediately triggered, bringing to mind the original world's setting, plot, and key characters.

At this moment, Reiger's exceptional memory indeed played a significant role, allowing him to smoothly recall most of the details about that world; he couldn't say he remembered everything, but at least the important parts were recalled.

This was a world where the story was set during the Taisho era.

The Taisho era, which was from July 30, 1912, to December 25, 1926, a total of fifteen years.

For Reiger, who had lived until after the year 2020 in his previous life, that was an era over a hundred years ago.

In that era, there was a group of swordsmen who fought against monsters that traced back a thousand years, all in the shadows, unknown to everyone.

These weren't the monsters of the Earth Mistake World, who were driven into the underground city and couldn't return to the surface, but rather humanoid monsters who fed on humans and thus sustained themselves—'Demons.'

The demons fed on humans, devouring their flesh and blood, taking their lives without a shred of humanity, extremely brutal, and creating numerous tragedies.

Most people were unaware of their existence, those who knew typically either died by their hands or had suffered greatly at their hands, experiencing firsthand the tragedies created by the demons.

Therefore, these people spontaneously formed groups, banded together, took up their swords, and were determined to eliminate all the demons in the world.

This was the main story of "Demon Slayer," revolving around the struggle between the demons and the Ghost Hunters, composing a somewhat splendid and somewhat sad legend.

"If it's this world..."

Reiger felt a mix of excitement and apprehension.

The excitement came from the fact that there were some power systems in this world that interested him.

The worry was because although there were demons to hunt, if he remembered correctly, demons were not the kind of numerous creatures that would allow Reiger to grow rapidly by slaying large numbers of them like in the Earth Mistake World.

"The time ratio is 1:180, huh?"

In other words, Reiger could stay in that world for a total of six months, a full half-year.

Half a year seemed like a long time, even longer than the time Reiger had spent since his transmigration, but whether he could accumulate enough to level up within this half-year in that world was an uncertainty.

Fortunately, in that world, there were some things worth exploring.

Thinking of the power system in that world, a few sparks of inspiration flashed through Reiger's mind.

"Perhaps I can give it a try."

If the thoughts in his mind could be realized, then Reiger might gain a completely new battle capability.

"Even if I fail, the effort of half a year's time will definitely lead to growth, it won't be in vain."

With that thought, Reiger firmed up his resolve, lay down, and closed his eyes.

A while later, Reiger's breathing steadied, as if he had entered into a dream.

However, Reiger's consciousness was no longer here, but had traveled through the dimensional passage constructed in his mind to another world.

The room immediately quieted down, leaving only the sound of Reiger's breathing rising and falling, creating a tranquil atmosphere.