Isekai Adventure in the Dimensional Cube

Reiger's speculation was not without foundation.

The Total Concentration Breathing technique already had the effect of enhancing physical abilities, but it only strengthened the cardiopulmonary capacity, speeding up blood flow to indirectly increase the body's vitality and physical capabilities.

In the Akasha continent, breathing techniques aided in cultivating skills, activating Magic Power, and revitalizing the body, allowing the body to grow holistically by absorbing Magic Power. If this principle could be integrated into Total Concentration Breathing, then it was not impossible to expand the enhancement scope of Total Concentration Breathing to all aspects of the body.

The breathing method of the Akasha continent could also stimulate Magic Power and activate it. If this aspect were also integrated into Total Concentration Breathing, allowing the activated Magic Power to blend into the rapidly flowing blood, enhancing its intensity and effect, then Reiger would definitely gain more improvement and greater strength when using the breathing method.

This was a process of mutual corroboration, integration, and supplementation. As long as the two could be cleverly combined, Reiger's speculation would not be mere fantasy.

For this reason, Reiger had chosen the Sun Breathing technique as his foundation.

The Sun Breathing technique could derive various other breathing methods, and its essential role as the progenitor and basis of breathing techniques was evident from its immense inclusivity.

With the highly inclusive Sun Breathing as the foundation, and the fusion of the breathing methods and sword skills from two worlds, the success rate would greatly increase.

Reiger also had the Five Basic Breathing Techniques as a reference. Each of these fundamental techniques had unique characteristics; some had the ultimate enhancement in speed, while others significantly increased flexibility. By drawing on them, Reiger might expand the range of enhancement of the breathing method to every part of the body.

Additionally, with Reiger's mastery of the Steel-Breaking Sword Skill and the incomplete Holy Dragon Sword Skill, the full integration of the breathing methods of the two worlds into the Sun Breathing technique to unprecedentedly boost its strength was entirely feasible.

Mastering the Sun was not just a figure of speech; it was indeed Reiger's goal.

With the Holy Dragon Sword Skill, which reputedly conditioned one into a dragon as a reference, if Reiger could endow the transformed Sun Breathing with the effect of honing oneself, his physique might truly undergo an unprecedented transformation.

In that case, if practicing the Holy Dragon Sword Skill transforms one into a dragon, wouldn't practicing the Sun Breathing turn one into the sun itself?

Of course, for now, this was merely a wishful thought, and Reiger did not know if it could be achieved.

But integrating breathing methods of the two worlds into Sun Breathing was something he was somewhat confident about.

If this idea were to work, his gains in this world would indeed be worth the price of admission.

Imagine, if the transformed Sun Breathing could enhance every single cell in the body and even utilize the immense Magic Power within Reiger, turning it into a tangible force to strengthen the body, how strong would Reiger become?

Certainly not weaker than when using the Wind Spirit Swift Walk, right?

More importantly, Total Concentration Breathing held a special realm of mastery.

It was a state in which one could remain fully focused even during sleep, maintaining the breathing technique and keeping the body perpetually enhanced, known as Total Concentration: Constant.

Swordsmen skilled at Total Concentration: Constant were among the top fighters in the Demon Slaying Corps, and mastering it was also the minimum requirement to approach the power of the Pillars.

If Reiger's idea succeeded, then he could master the entirely new state of Total Concentration: Constant for Sun Breathing, essentially using Sun Breathing and practicing sword skills at all times.

What did this mean?

It meant that even in his sleep, without actively training, Reiger could become stronger at every moment!

Thus, even if Reiger could not amass experience points by slaying a multitude of monsters in the underground city of the Earth Mistake World as he previously had, his constant training would rapidly increase his abilities!

This method might not enable Reiger to achieve level ups as feats of greatness, but it could help him reach the upper limit of his current level at the fastest speed, that is, the all-powerful SSS stage!

"Is it really possible to succeed?"

Imagination was beautiful, and Reiger believed there was nothing wrong with his idea, but whether he could successfully merge the breathing methods of the two worlds into a brand new Sun Breathing technique, he naturally did not know.

"But, I have to try."

In Reiger's mind began to emerge the principles of Sun Breathing, the Five Basic Breaths, the Steel-Breaking Sword Skill, and the Holy Dragon Sword Skill; he closed his eyes.

"Breath—in—and out—"

Gradually, Reiger began to regulate his breathing.

......

Frankly, the process of attempting integration was painful.

Reiger had to continuously adjust his breathing, constantly experiment with the effects of various breathing techniques, and then assimilate, combine, and even modify them. This had a significant impact on his body.

Completely disordered breathing sometimes made Reiger feel as though his lungs were about to explode and his airways were burning, an especially excruciating pain.

During this process, he frequently experienced symptoms like tinnitus, sore throat, tightness in the chest, swollen veins, and muscle tears, which frankly felt almost like torture.

Reiger gritted his teeth and persevered, even recklessly disregarding his own body.

After all, with the high-level healing magic of "Diya Flatel" at hand, as long as his limbs didn't explode or his heart and brain didn't burst, Reiger could bring himself back to life, so he adopted the mindset "as long as it doesn't kill me, torture me to the brink," enduring the pain and persisting in his effort.

Whether the Sun Breathing could evolve as envisioned would have a substantial impact on Reiger's future and his strength.

If he didn't persist at this time, then he would no longer be Reiger.

"Is this also a kind of challenge?"

Reiger was always a tough one; otherwise, he wouldn't have been so driven before, constantly pushing the limits of the human body, always seeking thrills.

If enduring a bit of torment and pain meant success, then it was definitely a win for Reiger.

So, Reiger kept trying and persisting, combining all his understandings and concepts of breathing techniques in his mind.

Eventually, Reiger successfully lost track of time and even forgot to eat and sleep, standing in the courtyard for a whole day and night.

"Breathe—Inhale—"

In the courtyard, the sound of breathing varied, tuned, and changed continuously.

During this period, Kyoujurou Rengoku came to take a glance, as did the trio of protagonists, and they all didn't dare disturb Reiger, letting him continue his attempts there.

One day...

Two days...

Three days...

In the blink of an eye, several days passed, and Reiger maintained the same stance from beginning to end, never moving an inch.

That day, Tanjirou finally couldn't hold back any longer.

"Mr. Rengoku, are you really not going to stop Mr. Reiger?" Tanjirou stood at the entrance of the courtyard, looking at Reiger's back turned towards them, and said worriedly to Kyoujurou Rengoku beside him, "He hasn't eaten or drunk for several days; his body will break down at this rate."

"Hmm, that is indeed a serious concern," Kyoujurou Rengoku said, watching Reiger intently. "The problem is, we can't stop a person from advancing toward a higher realm."

"To advance to a higher realm, one still needs to eat, rest as well," Tanjirou said. "Can't he eat well, rest well, and then strive forward?"

Tanjirou himself was a very hardworking person. Originally, to master the Water Breathing technique and become a Ghost Hunter of the Demon Slaying Corps, he had trained in the deep mountains for two consecutive years, his hands chafed to bleeding countless times, and he sustained innumerable injuries on his body. The hardship of it all was clearer to him than anyone else.

Moreover, after experiencing the ordeal of the Lower Five, Tanjirou had also undergone the Full Focus, Constant training with the Insect Pillar, which was equally extreme in difficulty.

And Tanjirou had persevered through it, so he knew very well that the harder one tries, the greater the rewards one can reap.

But even he would not go to the extent of not eating, drinking, or sleeping—in the literal sense of the word, neglecting all else for his training.

This was too worrying, and Tanjirou couldn't help but speak out.

"I know what you're thinking, and I'm worried too," Kyoujurou Rengoku said, patting Tanjirou's shoulder. "But take a closer look at that figure, can you really rush up and stop him?"

Tanjirou fell silent.

Reiger's silhouette looked so desolate, so lonely, yet for some reason, anyone who gazed at that figure could perceive an unwavering, uncompromising determination.

Tanjirou's sense of smell was still very acute; through the scent coming off Reiger's body, he could tell how hard, how painful it was for him.

Otherwise, why would there be the smell of sweat and even blood emanating from Reiger, who simply stood there?

He was definitely undergoing a type of training impossible for others to understand, yet exceedingly grueling.

"From the rhythm of his breath, one can tell that he is currently trying something," Kyoujurou Rengoku said. "It's a very dangerous attempt just listening to that breathing makes me uneasy, yet he's still persisting. I think what he's trying now must be very important to him, right?"

With that being the case, Kyoujurou Rengoku couldn't step forward to stop him.

"Let's have faith in him, young Tanjirou," Kyoujurou Rengoku said with a smile to Tanjirou. "Mr. Reiger is a very incredible person; I felt that when I first saw him on the Infinite Train, and the lord must also have seen something in him; that's why he chose to help him tirelessly."

"Let us trust him and wait here for his success."

Kyoujurou Rengoku's words made Tanjirou turn his gaze back to Reiger.

A moment later, Tanjirou slapped his face.

"I've got to work hard too!"

Tanjirou turned and left, heading back to train.

Kyoujurou Rengoku watched this unfold, reflecting.

"Such good young men," he sighed.

Pity, he hadn't been able to take them as his successors.

"No, forget Mr. Reiger, but maybe I could try with young Tanjirou?"

Suddenly, Kyoujurou Rengoku stroked his chin, considering this idea.

Unaware of all this, Reiger was still there attempting, not stopping for even a moment.