Isekai Adventure in the Dimensional Cube

"Long time no see, Mr. Tsukiguni!"

Excitedly, Tanjirou greeted Reiger.

"Hello." Reiger nodded at Tanjirou, saying, "It has indeed been a long time."

When Reiger was first hosted by the Rengoku family, he and Tanjirou used to meet frequently, but since Reiger began developing an entirely new breathing technique, attempting to evolve the Sun Breathing, he hadn't seen much of Tanjirou.

Tanjirou did often come to see what Reiger was up to when he was working on evolving the breathing techniques, but by then Reiger had devoted his entire being to trying out the new methods, neither seeing Tanjirou nor greeting him.

And after Reiger completed the evolution of the Sun Breathing, Tanjirou had left on a mission and wasn't at headquarters.

So, counting carefully, the two hadn't seen each other for at least one or two months, which could justifiably be called a long time.

After one or two months, there hadn't been any significant changes in Tanjirou, except that his breathing had become much more balanced and stable, proving that he had not neglected his training during this time, and his strength continued to grow steadily.

"You've come to the Swordsmith Village too?"

Reiger said it as a matter of fact.

"Yes." Tanjirou nodded repeatedly and said, "Mr. Rengoku told me to train here, saying a big final battle might be coming, and if I didn't want to be left out, I should boost my strength now."

At this point, Tanjirou cast an admiring glance at Reiger.

"I saw the combat training just now. You're amazing, Mr. Tsukiguni; even though the pillars are so strong, you alone overpowered them..."

Although Tanjirou knew Reiger was strong, after all, he wouldn't have been able to decapitate Akaza, one of the Upper Moons, on the Infinite Train with a single strike, he didn't expect that in just a few months not only had Reiger become so much stronger, but he had also become the chief instructor of the Ghost Hunters.

He had heard that the chief instructor holds a position above that of the pillars, equal to the lord!

...Was it too rude of me to greet him so directly just now?

Should I kneel down and bow my head even lower than my knees?

Fortunately, Reiger spoke in time, interrupting Tanjirou's wayward thoughts.

"You're not bad yourself." Reiger glanced at Tanjirou and said, "I can feel that you've gotten much stronger than before, you must be close to the pillar level now, right?"

Reiger wasn't just making empty talk.

Tanjirou had already learned Total Concentration: Constant during the Infinite Train incident.

Total Concentration: Constant is the minimum condition to approach the strength of the pillars. Once mastered, it's possible to rapidly catch up to the pillar level.

After the incident on the Infinite Train, Tanjirou became the adoptive son of Rengoku Kyoujurou, and while Reiger was evolving the breathing technique, Tanjirou also received plenty of guidance from Rengoku Kyoujurou, indeed becoming much stronger than before. Even if he hadn't reached the pillar level yet, he wasn't far off.

Currently, Tanjirou was about equivalent to the ultimate Lv. 3, just a step away from stepping into the Lv. 4 pillar level.

With such a level of strength, putting aside the Upper Moon demons, the Lower Moons definitely weren't Tanjirou's match anymore.

If Tanjirou could unlock the Demon Slayer Marks like in the original story, he should immediately gain strength equivalent to that of a pillar, right?

Unfortunately, the marks come at a great risk, and Reiger did not wish to harm this innocent and kind young boy, so it was better not to.

"No, no, no, I'm still far from it."

Tanjirou waved his hands in protest, not daring to accept such high praise from Reiger.

Reiger didn't mind and casually asked, "Where are your two companions? Didn't they come with you to the Swordsmith Village?"

"Are you talking about Zenitsu and Inosuke? They did come!" Tanjirou reported truthfully and said, "But Inosuke said he wanted to defeat the wild boars and bears around here, so he went into the mountains and has been missing, and Zenitsu received a letter yesterday that made him look really terrible. He also disappeared this morning."

"...Is that so?" Reiger's tone paused before returning to normal, "What about your sister? You didn't bring her out?"

Reiger pointed to Tanjirou's empty back.

There, where he used to carry the box that he never parted with, was now equally absent.

"Ahaha..." Tanjirou chuckled awkwardly, saying embarrassedly, "Nezuko can't be exposed to sunlight, and since I came for training, I just left her at the dorm."

"Alright." Reiger nodded, showing understanding, and then said, "Since you're here to train, go find Rengoku. He's resting over there."

Having said that, Reiger prepared to leave again.

"Wait, Mr. Tsukiguni." Tanjirou quickly called out to Reiger again, adding, "May I ask you something?"

Hearing this, Reiger stopped in his tracks.

He turned around, looked at Tanjirou, and suddenly smiled.

"Are you wanting to ask about the Sun Breathing?"

Reiger seemed to have seen through Tanjirou's heart as he said this.

"You, you already know?"

Tanjirou was momentarily taken aback.

"Sort of." Reiger said with a half-smile, "Ever since the end of the Infinite Train incident, I thought you might ask me about this. I didn't expect you to hold out until now."

Tanjirou grinned sheepishly and said, "I just never found the right opportunity..."

"Then ask now," Reiger said, crossing his arms, "I'll tell you what I know."

"Thank you!"

Tanjirou was overjoyed and quickly expressed his thanks.

"No need, it's just a trifle," Reiger replied and shook his head.

"Then I won't stand on ceremony," Tanjirou said seriously, looking at Reiger, he finally asked the question that had been pressing on his mind for several months. "May I ask, do you know about the Fire God Shen Yue Dance?"

"I do," Reiger nodded frankly. "That's the dance passed down from generation to generation in your family, right?"

"Yes," Tanjirou took a deep breath and said, "My family has been living on the mountain selling charcoal. For a very long time, they have survived by selling charcoal, and it's said that this trade has been in my family for several hundreds of years."

"I used to have a father and a mother, as well as many younger brothers and sisters."

As he spoke, a look of reminiscence and pain appeared on Tanjirou's face.

"But two years ago, Kibutsuji Muzan attacked my family. He killed my family members and turned my sister Nezuko into a demon."

This painful past was something Reiger, who was familiar with the original story, knew all about.

Originally, Tanjirou had a very happy and ordinary life, just like most people, an insignificant ordinary person in this world.

His father had been bedridden for years and passed away quite quickly, leaving the family behind. But before the demon attack, the Kamado family had been living a happy life.

It wasn't until Kibutsuji Muzan attacked the Kamado family, killing everyone in the household, that Tanjirou's ordinary and happy life was completely ended.

Tanjirou, by chance, escaped the tragedy because he was down the mountain selling charcoal, but all his family members died, leaving only his sister—Kamado Nezuko.

But Kamado Nezuko had been turned into a demon by Kibutsuji Muzan, becoming a monstrous creature that feeds on humans.

If it hadn't been for the deep bond between Tanjirou and Nezuko, and Tanjirou's success in awakening Nezuko's humanity to prevent her from consuming humans, perhaps his sister would have become a monster that had to be eliminated by Ghost Hunters.

"My condolences," was all Reiger could say, as he wasn't good at offering comfort. He simply patted Tanjirou's shoulder.

"Thank you, please be assured, I have learned to move forward and not to immerse myself in the sadness of the past," Tanjirou said as he wiped the corner of his eyes before bringing up the important matter again. "Although my family sold charcoal, every year we performed the Shen Yue Dance as an offering to the Fire God."

"The Fire God Shen Yue Dance is the dance passed down through generations in my family, specially used to worship the Fire God," Tanjirou explained.

What Tanjirou wanted to inquire about was this Shen Yue Dance that was passed down through his family.

"I happened to use the Fire God Shen Yue Dance in battle and discovered that it is a very powerful breathing style," he said.

"So, I've always been puzzled, why would the Shen Yue Dance passed down in my family become a breathing style?" Tanjirou asked.

"And..." he hesitated.

Seeing this, Reiger continued Tanjirou's train of thought.

"And after seeing my battle, you realized that your family's Shen Yue Dance is identical to the Sun Breathing technique I use, right?" Reiger posited.

This made Tanjirou nod repeatedly.

"I have learned from Mr. Rengoku that Sun Breathing is the ancestral breathing technique, the original and the most powerful of all. But why is my family's Shen Yue Dance so similar to such an incredible thing?" Tanjirou was clearly puzzled.

In fact, this question had already been posed by Tanjirou to Rengoku Kyoujurou.

And the answer he received truly astonished him.

Now, Reiger was giving the same answer.

"You must have realized it by now, right?" Reiger looked directly at Tanjirou and smiled. "Actually, the Fire God Shen Yue Dance is the Sun Breathing technique."

"You already knew the answer, you just couldn't bring yourself to believe it," he stated.

"Am I right?"

Yes, it was exactly that.

Having become the adopted child of Rengoku Kyoujurou, Tanjirou had already inquired about his family's Fire God Shen Yue Dance and had even demonstrated it in front of Rengoku Kyoujurou, ultimately obtaining a confirmation from him.

"This is the Sun Breathing technique used by Tsukiguni Yoriichi!" Rengoku Kyoujurou had said with certainty.

But how could it be?

Why would the Shen Yue Dance of his charcoal-selling family be an ancestral breathing technique?

The answer, in fact, was quite simple.

"Your Kamado family has always been the inheritors of Sun Breathing," Reiger revealed the secret.

"During the Sengoku period, the founder of Sun Breathing, Tsukiguni Yoriichi, had a good relationship with your ancestors and demonstrated all forms of Sun Breathing to them."

"That's why your family has been passing down Sun Breathing as a Shen Yue Dance to worship the Fire God, generation after generation."

"Even the Hanafuda earrings that you wear, they were indeed Tsukiguni Yoriichi's own, given to your ancestor by him."

So, the Kamado family's Fire God Shen Yue Dance turned out to be Sun Breathing.