Isekai Adventure in the Dimensional Cube

———「Transparent World」.

This is a world or a state that can only be seen after putting forth one's full effort, enduring the pain, and making one's mind transparent.

Those who enter this state can, by concentrating and shutting down superfluous senses, make living bodies appear transparent as if seeing through the condition of the opponent's body, thereby observing the flow of blood vessels in the lungs, the contraction of muscles, the activity of organs, and so on, to predict and perceive the opponent's actions, significantly improving their own speed of movement, prediction of attacks, and evasion abilities.

In simple terms, this is an ultimate sublimation, control, and extension of senses.

Those who master the Transparent World can not only hide their fighting qi according to their own needs but also accelerate their perception, making the enemy's actions appear very slow, and the enemy's movements almost have no secrets in their eyes.

This is the Supreme Domain that Akaza, the Upper Moon Three, had mentioned, a final scene that masters of swordsmanship and martial arts have a chance to witness after having honed their skills to the limit.

Reiger reached this domain unknowingly in the three months of desperate perseverance.

So, once Reiger concentrates and shuts down his superfluous senses, focusing all perception on what's before him, he can make his mind transparent like this and easily observe the vital signs of the person in front of him.

For Reiger, this technique was quite useful.

After all, he didn't have any outstanding aspect in sensing abilities, at most he was more sensitive to the flow of wind and the atmosphere when using "Wind Spirit Swift Walk", or he was responsive to the flow of Magic Power.

Now that he had mastered the Transparent World, Reiger's perception would be hugely beneficial in battle, making fighting more worry-free and effortless.

This was a pleasant surprise, brightening Reiger's mood.

Unaware that they had been completely seen through, Rengoku Kyoujurou and Kochou Shinobu were still curious about Reiger's current strength.

"Just how strong has our lord become now?" Kochou Shinobu asked half-jokingly, "Is there no one left in this world who can stand as his opponent?"

"The young lord who can easily behead an Upper Moon has become even stronger," Rengoku Kyoujurou murmured, "Does our lord expect this?"

In that moment, Rengoku Kyoujurou and Kochou Shinobu both thought of Ubuyashiki Kagaya's words.

"I can already feel it, that within our generation, the Demon Slayer Corps and the demons may finally settle the battle and end this mistaken history that has continued for thousands of years."

Remembering the words spoken by Ubuyashiki Kagaya in a rare burst of excitement, Rengoku Kyoujurou and Kochou Shinobu exchanged meaningful glances.

Now, they might share the same feeling as Ubuyashiki Kagaya.

After all, they had seen with their own eyes the astonishing phenomena that occurred after Reiger succeeded in his training.

With his current strength, should there be an opportunity, he indeed might be able to settle the mistaken history that has continued for thousands of years, deciding the ultimate battle between the demons and the Demon Slayer Corps.

Thinking this, the way Rengoku Kyoujurou and Kochou Shinobu looked at Reiger changed.

"Thank you both for your help during this time," Reiger said, expressing his gratitude to them, "Without you, I might not have been able to complete the evolution of Breath of the Sun so easily."

"No, it really has nothing much to do with us, young lord!" Rengoku Kyoujurou disclaimed any credit, saying, "We haven't been of any help at all, all of this, you achieved through your own efforts!"

"That's true," Kochou Shinobu's tone also became somewhat wistful, "Lord Successor didn't need anyone to take care of him at my place. Even though you looked terrible each time you fell, you would wake up as if nothing happened. Besides providing a bed, it seems like I didn't do anything."

Rengoku Kyoujurou nodded seriously in agreement beside her.

He, too, had done nothing more than move Reiger into a bed and send him to the Butterfly Mansion to rest when he collapsed, at most providing Reiger with a place to exert himself freely.

But such a thing was not worth mentioning in Rengoku Kyoujurou's view.

Of course, Reiger definitely didn't see it that way.

"You both have taken care of me, that's a fact, no need to be modest," Reiger shook his head and said, "Anyway, I owe you both a favor. If you ever need my help, please don't hesitate to ask in the future."

This was Reiger's promise.

Kochou Shinobu seemed somewhat intrigued by this.

"Then may I ask Lord Successor to let me study your body?"

The woman finally revealed her ambitious desire.

"No."

Reiger didn't even think before refusing outright.

"Tch."

Kochou Shinobu pouted, looking disappointed.

"Please make a reasonable request, thank you."

Reiger sighed.

"Alright, I'll remember that,"

Kochou Shinobu replied with a smile, her words lacking any persuasive power.

"Then, young lord, do you plan to continue your training?"

Rengoku Kyoujurou tentatively posed this question to Reiger.

"I don't think it's necessary," Reiger considered, then added, "The breathing technique I envisioned has been realized, there's no need to continue training. If there's anything else I should do, it would probably be to attempt mastering Full Concentration, Constant,"

"Total Concentration: Constant?" Rengoku Kyoujurou nodded and said, "With your capability, young Finn, you should be able to master it very soon."

Reiger did not deny this statement.

For him, Total Concentration: Constant was indeed not a difficult task.

Not to mention his extraordinary learning ability and growth rate, Reiger also had the experience of venturing into the underground city to draw upon.

When venturing into the underground city, adventurers would need to rest and sleep within the labyrinth for up to several days at a time.

Sleeping in the dungeon filled with monsters was a challenge in itself, requiring not only that one calms their spirit and sleeps peacefully but also maintains constant vigilance, never completely relaxing even in slumber.

Even with companions standing watch, adventurers had to keep a minimal level of awareness of their surroundings to avoid sudden dangers.

Therefore, all high-level adventurers mastered a crucial skill: falling asleep quickly while maintaining a vigil during their sleep.

Finn had guided Reiger in this aspect during his first expedition to the underground city.

Thus, maintaining full concentration even while sleeping, keeping the breathing of concentration uninterrupted for twenty-four hours, was something Reiger could accomplish with some adaptation.

Once achieved, Reiger would be able to master the skill of Total Concentration: Constant, remaining enhanced by the breathing technique at all times and, equivalently, continuously honing his swordsmanship.

In this way, Reiger's initial concept of uninterrupted growth for twenty-four hours, which could tap into his potential and raise his stats without training, would become a reality.

"By the way, young Finn,"

At this moment, Rengoku Kyoujurou remembered something.

"The matter you entrusted me with, I have also taken care of it."

Hearing this, Reiger was momentarily startled, then quickly understood.

"Are you talking about the crimson sand iron and the crimson ore?"

Reiger's question was met with an affirmative response.

"Exactly," Rengoku Kyoujurou said with a grin, "Shall we go take a look?"

"Sure," Reiger replied without hesitation, nodding his head.

"Then I'll head back first," Kochou Shinobu said with a smile, "I'll report to our lord about young Finn's completion of his training. He should be delighted."

"Thank you, Kochou!" Rengoku Kyoujurou replied to Kochou Shinobu.

Kochou Shinobu then left, her smile lingering.

"Let's go, young Finn."

Rengoku Kyoujurou led Reiger into the residence.

As for the courtyard, people soon came over to put out the fire and clean up.

......

"How about this? Is this enough?"

In a warehouse of the Rengoku Family, Rengoku Kyoujurou sought confirmation from Reiger standing beside him.

Reiger did not respond immediately but instead observed the scene before him.

The sizable warehouse was filled with rocks that gleamed like jade and steel, piled up into small hills.

"Is this the crimson sand iron and crimson ore?"

Reiger murmured to himself.

"Yes!" Rengoku Kyoujurou exclaimed, "These are ores that can only be mined from mountains closest to the sun, bathed in sunlight all year round, absorbing ample sunlight, and they are the main material for forging Sun Wheel Blades!"

Without Rengoku Kyoujurou's explanation, Reiger could already sense the mild energy radiating from the ores, similar to sunlight.

This energy did not enhance the quality of the ores nor affect their structure. It could be said to serve a special purpose only against demons that fear sunlight.

Using these ores for sword-making, the resulting blades would not be much different from ordinary ones, except they had extra efficacy against demons.

If one were to leave this world, or rather, no longer face demons as adversaries, then the swords forged from these ores would be utterly ordinary, not cutting through iron like mud, perhaps even requiring a highly skilled Swordsman to successfully cut through rock.

However, in Reiger's hands, these many ores could still serve an extraordinary purpose.

"Then I'll accept them," Reiger once again thanked Rengoku Kyoujurou.

Rengoku Kyoujurou then departed, leaving Reiger alone with the warehouse full of crimson sand iron and ore. He approached them.

"Now then, let's begin."

A wave of Magic Power emanated from Reiger.