Isekai Adventure in the Dimensional Cube

Over the course of one week, although the Demon Slayer Corps' training ground hadn't expanded enough to accommodate many members at once, it was still no problem to let a dozen people enter and create a ruckus.

So, Reiger took all the pillars there, to this place surrounded by countless trees, where corners were piled with lumber that had been chopped down.

"Is it here?" Uzui Tengen looked at the undeveloped wasteland with a hint of disdain, "Such a place is not glamorous at all."

"Well..." Kanroji Mitsuri said while sweating, "I think even if it were glamorous, it wouldn't be useful..."

"This must have been jointly cleared by the swordsmiths village people and the members of the Hidden, right?" Rengoku Kyoujurou looked around and exclaimed loudly, "Hmm! Good! They've worked hard!"

"Before long, this place should be officially put to use." Kochou Shinobu explained to everyone, "Then, all members from the swordsmiths village can train here."

"It doesn't matter to me." Shinazugawa Sanemi coldly said, "The quality of the Demon Slayer Corps' members has been declining severely recently. How much can they really improve by cramming at the last minute like this?"

"I agree." Iguro Obanai played with the white snake around his neck and said, "Instead of letting weak members join the upcoming battle and wastefully lose their lives, it's better to exclude them from the fight right from the start."

"That's not good." Himejima Gyoumei clasped his hands together and said tearfully, "The members joined the Demon Slayer Corps because they wish to kill demons or have lost loved ones to them, or had important people eaten by them. In the coming decisive battle, excluding them would undoubtedly lead to much resistance. If this causes disarray within the Demon Slayer Corps before the battle, the losses would outweigh the gains."

The pillars immediately began to voice their own opinions, and for a moment, a bit of dispute arose.

Only Tomioka Giyuu and Tokitou Muichirou silently stood to the side, one silent and the other daydreaming, completely uninvolved in the pillars' argument.

Reiger naturally had no interest in discussing the Demon Slayer Corps' internal affairs with the pillars here.

"You guys can discuss these matters once you return." Reiger said, "Instead of worrying about the ordinary members, you might as well worry about yourselves first."

"Whether you can activate the marks, the burning blades, awaken the world of clarity, all these are still unknown. Do you even have the leisure to worry about others?"

With that, the pillars fell silent all at once.

"What should we do?"

Tomioka Giyuu, rarely speaking out, turned the topic back to its original direction.

"Don't rush." Reiger said calmly, "I still need to consider which ability you should try to awaken first."

As soon as these words were spoken, several pillars immediately responded.

"Is there even a need to think about it?" Shinazugawa Sanemi said, "Of course, we should activate the marks first!"

"Exactly." Iguro Obanai softly said, "Activating the marks, which can directly increase power, is most crucial for us."

Reiger might not care about the marks, but for the pillars, the marks were the most valued of the three abilities.

Although the burning blade could increase the damage against demons, it couldn't directly enhance strength. Solely relying on this ability against upper rank demons might not give an advantage.

The world of clarity was the same, the supreme domain that could enhance sensory and perceptual abilities was certainly powerful, but compared to the marks, which could directly enhance personal strength, it was less prioritized.

Therefore, the strength of the marks was the most valued ability by the pillars, and the ability they most desired to have.

If they couldn't activate all three abilities by the time of the great battle, and could only have one of the three, they would prefer that the one ability they were able to activate was the marks.

As for the severe side effects of the marks, it was almost considered nonexistent in the minds of the resolved pillars.

"Marks, huh?" Reiger looked deeply at the pillars before saying, "As much as I would like to praise your choice, activating the marks is not easy."

"Just tell us! Tsukiguni Head... Tsukiguni Grandmaster!" Rengoku Kyoujurou fearlessly addressed Reiger loudly, "What should we do to activate the marks?"

"It's simple." Reiger, not hiding anything, stated bluntly, "Normally, if one wants to activate marks, just raising the body temperature to 39 degrees and having a heart rate of over 200 beats per minute will suffice."

Upon hearing this, the pillars were momentarily stunned.

"Body temperature of 39 degrees?"

"Heart rate over 200 beats per minute?"

"...That's it?"

The pillars couldn't help but utter these words.

Not because of anything else, but because it sounded too simple.

Indeed, raising one's body temperature to 39 degrees and heart rate to over 200, was a huge challenge to the body's endurance.

But the pillars had assumed that activating the marks would require a very special method, one that was difficult to achieve.

Otherwise, how could it be that not a single swordsman with activated marks had appeared in the Demon Slayer Corps over the years, leading to the disconnection of this tradition?

But now, Reiger told them that just by raising the body temperature to 39 degrees and heart rate to 200, the marks could be activated. This truly puzzled the pillars.

"I know what you're thinking." Reiger, seeing confusion in the eyes of the pillars, said, "Such conditions might not be easily met by ordinary people, but for you, raising your body temperature to 39 degrees and getting your heart rate to over 200 during battle is not very difficult."

"However, these are indeed the conditions for activating the marks, without a doubt."

The original text had already made this very clear, so the conditions for activating the marks are just that, no question about it.

The problem is...

"Why are such simple conditions not met by anyone in the Demon Slayer Corps, yet not a single person who activated the marks is found?"

About this point, Reiger was also puzzled.

In his view today, raising one's body temperature to 39 degrees and increasing the heart rate to over 200 times per minute in battle was something any pillar could easily do.

The evidence lay in the original story where, after learning the conditions to activate the marks, all pillars almost effortlessly activated their marks in battle without even needing to try.

Reiger didn't believe that in so many past battles, no one had coincidentally raised their body temperature to 39 degrees and increased their heart rate beyond 200 times.

Yet, the truth was, ever since the first generation of breath technique swordsmen perished due to the side effects of the marks, almost no one in the Demon Slayer Corps had successfully activated a mark again.

Why was that?

Reiger thought of a reason.

"The marks have a characteristic."

Reiger explained to the pillars.

"Whenever someone successfully awakens a mark, it resonates in a way that enables those around them to activate their marks as well."

This was an exact description found in the records of the Ubuyashiki family.

Reiger recalled this and thus formulated a hypothesis.

"I believe the first person to activate a mark is crucial."

"The marks probably aren't that easy to activate; there must be some unknown conditions that need to be met."

"But once someone successfully awakens a mark, those around them should be able to activate theirs more easily."

This was Reiger's hypothesis.

This hypothesis had its foundations.

In the Warring States period, when Tsukiguni Yoriichi joined the Demon Slayer Corps, many of the original breath technique swordsmen in the corps started activating their marks.

In the original story, when Tanjirou joined the Demon Slayer Corps and successfully awakened his mark, pillars in the corps began to activate their marks easily using the method mentioned above.

Besides the times when these two joined the Demon Slayer Corps, the original story did not mention any era in the corps' history with a great number of mark swordsmen appearing.

Based on this, Reiger formulated his hypothesis.

"Perhaps, the first person who awakens a mark can only be a swordsman who masters the Sun Breathing technique."

"Or perhaps, the initial awakening of the marks involved some other existing conditions."

"Only when someone successfully activates a mark can those around them start to activate their own marks through the resonance of the mark."

Reiger thus informed the pillars.

"Based on this hypothesis, it might be very difficult for you to activate marks initially, only reducing in difficulty once one of you successfully awakens a mark."

Reiger's words made the pillars furrow their brows.

"Anyway, just give it a try first," Reiger decisively said, "try raising your body temperature to 39 degrees and increasing your heart rate to over 200 during battle to see if anything changes in your body, then decide what to do next."

With these words from Reiger, the pillars immediately relaxed their furrowed brows.

"So, we need to battle here first, right?"

Shinazugawa Sanemi immediately set his gaze on Rengoku Kyoujurou.

"You want me as your opponent, Shinazugawa?"

Rengoku Kyoujurou understood Shinazugawa Sanemi's intent.

"We have an unsettled score between us, don't we?"

Shinazugawa Sanemi was referring to the incident shortly after Rengoku Kyoujurou became the Flame Pillar, where the two had briefly clashed.

"I have no problem with that!"

Rengoku Kyoujurou readily agreed.

In the past, they indeed hadn't settled the score, as Rengoku Kyoujurou did not want to breach the corps rules.

Fighting against a fellow swordsman from the same team was forbidden in the Demon Slayer Corps, and naturally, Rengoku Kyoujurou did not want to act recklessly and violate this.

But now, if there was a reason to fight, then Rengoku Kyoujurou would not refuse.

"Very well."

Shinazugawa Sanemi revealed a ferocious smile.

At the same time, the other pillars prepared for paired-up battles.

Reiger stepped back a little and watched as the pillars partnered up, observing the battle.