Eventually, under the invitation of Kyoujurou, Riezel moved into the residence of the Rengoku family.
As a family of Demon Slayers for generations, the residence of the Rengoku family was kept strictly confidential. Since they had earned the trust of the Ubuyashiki family, their connection with the Demon Slayer Corps was strong enough to withstand scrutiny. Consequently, their residence was not very far from the Ubuyashiki Estate; one could even say it was in the same town.
Riezel couldn't help but suspect that this town was specifically established for the Demon Slayer Corps and those closely related to them.
Several Hashira had also moved to this town after retirement, though he wasn't sure where they had gone, it seemed plausible that they had established residences here.
If that were indeed the case, the financial resources of the Ubuyashiki family might surpass even his imagination, to create a whole town for residency, showcasing their immense wealth.
The Rengoku family was equally impressive, boasting a rich history, though not on par with the Ubuyashiki family, it was far greater than an average family.
After settling in, Riezel received a brief tour from Kyoujurou.
"My father and little brother also live here, but my father is currently semi-retired, and my little brother isn't a Demon Slayer yet, so I won't introduce them to you for now. Just relax and make yourself at home. If you want to practice, the courtyard is spacious enough!"
After the tour, Kyoujurou assigned a room to Riezel.
During this time, Riezel also encountered the three main characters, but they seemed to be engaged in some inexplicable training fervor.
"Hahaha! Let's settle this, Lord of the Land!" Inosuke excitedly chased after a humanoid locomotive figure in the courtyard.
"For fuck's sake! Why do I have to be the Lord of the Land!" Zenitsu, clad in a locomotive-shaped costume, yelled furiously while evading Inosuke's pursuit.
"334... 335... 336... 337..."
Meanwhile, Tanjirou was doing push-ups, seemingly focused on enhancing his stamina, while a wooden box rested on his back as a weight.
The three of them were making a ruckus in the courtyard, which amused both Riezel and Kyoujurou, who watched for quite some time.
"...Should we not disturb them?" Riezel suggested.
"Agreed." Kyoujurou replied with a serious expression.
And thus, Riezel temporarily settled in the Rengoku residence.
At the same time, the Ubuyashiki family acted swiftly, showing considerable importance to Riezel's request by sending over what he had asked for the very next day.
"Here you go, five books of fundamental breathing styles." Kyoujurou said with a smile as he handed over five books to Riezel.
Even though the five books were not thick, each of moderate thickness, they formed the foundation of the Demon Slayer Corps. The covers of the books were color-coded according to their respective breathing styles.
Flame Breathing was red.
Water Breathing was blue.
Stone Breathing was gray.
Wind Breathing was green.
Thunder Breathing was golden.
Five books with different colored covers were neatly arranged in front of Riezel, presenting an impressive sight.
"These five books are specially curated and updated to the latest editions, packed with insights from different experts. For example, Flame Breathing includes knowledge and explanations passed down from generations of Flame Hashira in my family!"
Kyoujurou grinned widely at Riezel.
"Though we can't arrange for those experts in other breathing styles to provide face-to-face guidance to you, if it's Flame Breathing, feel free to ask me anything if you're unclear!"
A direct guidance from the Flame Hashira himself, undoubtedly an invaluable opportunity for any average swordsman.
"Alright, thanks." Riezel didn't refuse outright, simply agreeing.
"Is there anything else I can do for you?" Kyoujurou exclaimed. "Master has already instructed me to fulfill all your requests as much as possible!"
Upon hearing that, Riezel pondered for a moment before making another request.
"Could you prepare Scarlet Crimson Iron Sand and Scarlet Ore for me?"
Naturally, he was referring to the metallic minerals used to forge Nichirin Swords.
"Oh?" Kyoujurou's eyes gleamed. "You need a Nichirin Sword?"
"I might..." Riezel chuckled and shrugged his shoulders. "After all, I don't have one yet, and using Sun Breathing with a Nichirin Sword seems to be a better match."
In this world, swords and katana were essentially the same weapons, otherwise, 'Breathing Style' wouldn't be referred to as 'swordsmanship'.
The difference between Nichirin Swords and the ones Riezel usually wielded, was that the former had only one sharp edge, while the latter had two. Additionally, the blade of Nichirin Swords was curved, suitable for heavy slashes, while the latter's blade was straight, allowing for more flexibility.
Both could be used for performing breathing styles, but they had their differences.
Even though, all of Sun Breathing's forms were supposed to be performed with a Nichirin Sword, if Riezel wanted to use different types of swords to perform it, he probably had to make some adjustments.
However, he didn't have any plan in that regard at the moment, since he simply thought that if he had a Nichirin Sword, it would at least be pretty useful when dealing with demons. Without it, he would have to rely on decomposition magic to kill demons.
However, since he decided to focus on studying breathing styles, he decided to temporarily refrain from using magic.
In that case, acquiring a Nichirin Sword was indeed necessary.
"Shall we take charge of forging your Nichirin Sword?" Kyoujurou asked, brimming with enthusiasm. "You know, the Corps has expert swordsmiths who work in secret, and their craftsmanship is excellent. They'll surely forge a Nichirin Sword that satisfies you!"
He was not boasting.
The Demon Slayer Corps indeed had a close collaboration with a group of swordsmiths who resided in Swordsmith Village. Almost all of them were swordsmiths, responsible not only for forging and maintaining all Nichirin Swords of Demon Slayers but also deeply passionate and dedicated to swordsmithing.
Generation after generation, they researched and forged Nichirin Swords, continuously improving their craftsmanship year by year. They were undoubtedly the elites of the swordsmithing industry.
Not only did each Demon Slayer have a dedicated swordsmith to forge their Nichirin Sword, but to prevent demon attacks, the location of Swordsmith Village was highly secretive, with hardly anyone in the Corps knowing its exact whereabouts.
Even entering the village required blindfolds and nose plugs, with several people specially designated to escort and guide, with the guidance of Kasugai Crows.
Moreover, the order of the route, the guiding Kasugai Crow, and the escorting people changed frequently, ensuring the utmost secrecy, comparable to the Ubuyashiki Estate, the headquarters of the Demon Slayer Corps.
It could be said that in this world, no smith was more skilled at forging Nichirin Swords than swordsmiths from Swordsmith Village. Even the swords of the Hashira were forged there, which was why Kyoujurou was so proud and eager to recommend them.
Unfortunately, Riezel had no intention of having swordsmiths from Swordsmith Village forge his sword.
"Just get those two materials ready for me and I'll handle the rest. I've got my own plans." Riezel answered calmly.
Indeed, there was no denying that in this world, Nichirin Swords were considered a particularly special weapon.
However, it was a different story in other worlds.
Whether it was in terms of hardness, power, sharpness, or even endurance, Nichirin Swords could only be considered an ordinary weapon, far from meeting the standards of 'special equipment' in the world of Danmachi.
In other words, Nichirin Swords couldn't even be classified as third-class equipment, just a relatively outstanding weapon among ordinary equipment.
It could inflict damage on demons, not due to the sword's performance, but because of the properties of the forging materials.
Capable of emitting energy similar to sunlight, it had a significant effect on demons, but it was utterly useless against anything other than demons.
Such a weapon was naturally not suitable for Riezel.
Even without using 'Ariel', with his current strength and level, there was a good chance the Nichirin Sword would break if he engaged in serious combat.
He remembered that Tanjirou's sword had been broken during the fight against the Lower Five, so he didn't want to use such a fragile sword.
It was undeniable that the swordsmiths in Swordsmith Village might have decent skills, but they were ultimately just ordinary people, unlike the advanced blacksmiths in the world of Danmachi.
Not only did these advanced blacksmiths possess the 'Blacksmith' development ability capable of adding special attributes to forged weapons, but they could also process special materials and forge weapons that could cut through the steel-like bodies of floor bosses.
If his Nichirin Sword were to be forged by the swordsmiths in Swordsmith Village, the result would only be an excellent sword, unable to even touch the edges of special equipment.
For Riezel, who possessed first-class and second-class equipment with the Durandal attribute, it was undoubtedly not a good sword.
For this reason, Riezel's thought was simple—he would forge the sword himself.
'I may not have the 'Blacksmith' development ability or know swordsmithing, but I have magic.'
He had learned structure system magic from Yuri, so while he couldn't make magic items or alchemy items, if it came to making weapons, he could still manage.
Of course, what he would make wouldn't be magic weapons, just ordinary weapons.
With his current level, accumulated 'MAG', and assistance from the 'Mage' development ability, the magic he wielded would undoubtedly surpass that of ordinary structure system magicians in terms of power and effectiveness.
'If I use decomposition magic to break down large quantities of Scarlet Crimson Iron Sand and Scarlet Ore, removing all impurities and leaving only the essence, the quality of these two materials would reach the standards of special materials.'
'Afterward, using structure system magic to merge the essences of the two materials with Hermit and transform them into a Nichirin Sword.'
'This way, the quality of my Nichirin Sword should be outstanding, right? By then, I could at least possess a Nichirin Sword with the Durandal attribute.'
With those thoughts in mind, Riezel had already decided.
If he was going to use a Nichirin Sword, then he wanted the best one.
One that surpassed the understanding of everyone in this world, an exclusive Nichirin Sword just for him!