Mugen Train.
The name sounded grand, easily leading one to believe it was something extraordinary.
However, in reality, the so-called Mugen Train merely referred to a train named 'Mugen (Infinity)'.
This train wasn't unknown; perhaps it was because trains in this era weren't as prevalent as in later years, so anything related to trains tended to make headlines in newspapers.
Recently, something peculiar happened on this train.
It was said that passengers aboard the Mugen Train, upon its arrival at the terminal station, inexplicably vanished.
Even though not everyone on the entire train disappeared at once, every so often, someone would board the train and then mysteriously disappear, with witnesses seeing them get on but no one witnessing them disembarking.
This incident caused quite a stir, making headlines several times and garnering significant attention.
As a result, a rumor began circulating that said 'Mugen Train will eat people'.
When Riezel saw the newspaper, the reason for the headline specifically mentioning 'man-eating' was apparent.
Thanks to this, the Mugen Train underwent repairs recently, only resuming service after maintenance workers confirmed there were no anomalies on board.
And so, today marked the Mugen Train's first journey back in service.
*Tooot!* *Tooot!*
As the loud whistle pierced the night, the Mugen Train, with its dark steel front and wooden carriages, rolled in from the other side of the rail tracks and halted at the platform.
People queued up orderly to board, entering the carriages and finding seats.
With a ticket in hand, Riezel quickly blended in and settled into a window seat, looking like an aspiring young man about to embark on a journey.
Behind him, a few passengers engaged in conversation.
"Is this the train that eats people?"
"Don't be crazy. How could there be a man-eating train in this world?"
"Well, if it were real, I'd totally wanna see which part of the train does the munching."
"Maybe it's the locomotive?"
"Hahaha..."
The passengers chatted and laughed, treating the man-eating train rumor as amusement.
On the other hand, Riezel remained calm and didn't turn to look at them.
If these passengers were characters in a horror film, they might be the first batch of sacrificial victims.
Ignoring the passengers' conversations, Riezel took out the bento he had bought at the station and prepared to fill his stomach.
Unexpectedly, as he opened the bento box, a loud voice echoed from behind.
"Don't underestimate it!"
It was genuinely a booming voice, enough to make one's eardrums ache.
"What the—!"
"Hey, who are you?!"
"Damn loud!"
A few passengers behind Riezel seemed to be startled by the sudden outburst.
However, the owner of the voice seemed not to pay attention to the reactions of the passengers, continuing to speak.
"Whenever rumors arise, there's always a reason! We must not treat potentially dangerous situations lightly! We must be extra careful, you hear me?! Everyone!"
As the voice's volume increased, the owner of the voice seemed deliberately intent on shouting, which attracted the attention of the surrounding passengers.
"What's wrong with this guy?"
"No idea..."
"Let's switch to another carriage."
Several passengers suddenly felt the need to keep their distance and quickly left, not staying in this carriage any longer.
Apparently, many passengers shared the same sentiment, causing the relatively crowded carriage to suddenly empty out quite a bit, becoming somewhat colder and silent.
Only then did Riezel lower his hands from covering his ears, partly narrow his eyes, and turn to look behind him.
In the next moment, a figure entered his field of vision.
It was a striking young man.
The young man had very conspicuous yellow hair, styled quite uniquely, resembling a burning flame, with even some edges of his hair dyed red.
He also had thick black eyebrows, sharp eyes, and wore a brown uniform with a white haori adorned with a feather pattern and flames at the edges, giving him a very unique appearance that clearly marked him as a unique character.
Of course, this was nothing compared to the large number of bento boxes the young man was carrying in his hands.
Seeing this unique young man and the large number of bento boxes he was carrying, Riezel couldn't help but silently remark to himself.
'Just boarded the train and already encountering an important character?'
The conspicuous and distinctive appearance of this young man allowed Riezel to recognize him with just a glance.
At the same time, paying no attention to the surrounding gazes, the young man continued to wear a smile, calling out to the passengers heading toward another carriage.
"Remember to be extra careful, and shout loudly if you encounter danger, okay?!"
His booming voice ultimately resulted in those few passengers running even faster.
Seeing this scene, the young man merely nodded in satisfaction, as if completing some mission, then turned and sat down.
The spot he chose to sit was exactly where those escaping passengers had been sitting, right behind Riezel.
Riezel didn't bother to look back at the young man, just lightly smiled and began eating his still-warm bento. It was a high-quality beef hotpot bento, albeit slightly cooled down, but it still carried a unique flavor.
Since arriving in this world last night, Riezel hadn't eaten a thing, so this bento came just in time to fill his stomach.
However, he wasn't fully focused on savoring the bento; instead, he mechanically ate while gradually shifting his attention to the young man behind him.
Even though he didn't turn around to look, Riezel could keenly sense that this young man's breathing was different from the others.
Specifically, the way he breathed was peculiar.
Whether in rhythm or frequency, this young man's breathing differed from that of normal people. While it might not be evident on the surface, in reality, he was inhaling a considerable amount of air into his lungs, yet exhaling very little. It made one wonder where all that air was being sent.
'So this is the breathing technique of this world?' Riezel pondered silently.
Indeed, this world also had its own breathing technique, known as 'Breathing Style'.
However, unlike the breathing style of the Akasha Continent, which was merely a supplementary method for swordsmen's practice, the breathing style of this world served as the main combat support, created to allow humans to confront demons with their frail bodies.
Its primary purpose was to enhance heart and lung function, drawing in large amounts of oxygen through a special breathing technique to accelerate blood circulation in a short time. This could significantly boost one's physical abilities in an instant, temporarily granting them physical prowess equivalent to that of demons.
Its full name was 'Total Concentration Breathing'.
One of the major reasons why the Demon Slayers in this world could contend with demons, engage in combat with them, and even subdue them, was this 'Total Concentration Breathing'.
Most people that were proficient in Total Concentration Breathing were members of an organization called the 'Demon Slayer Corps'.
At this moment, the young man sitting behind Riezel, who left a strong impression, was undoubtedly a Demon Slayer who had mastered a breathing style.
Listening to the breath of this young man, Riezel gradually had an idea.
'Is it like this?'
Riezel consciously adjusted his breathing to align with the young man.
For him, this wasn't difficult.
Due to his practice of Breaking Steel Sword Style, he had already specialized in breathing techniques. So even though it was a different world, with different effects and functions, his experiences allowed him to quickly grasp this world's breathing technique.
Moreover, having an example right near him, it didn't take long for Riezel to adjust his breathing frequency to be almost identical to that of the young man behind him.
In this split second, Riezel indeed felt the oxygen he inhaled into his body energizing his bloodstream, accelerating blood flow, and strengthening his heart and lungs, resulting in a surge of power within him.
'Interesting...'
Feeling all of this, Riezel's lips curled upward as he breathed in once again.
This strange sensation caused him to become somewhat immersed, momentarily ignoring the commotion around him.
However, soon enough, a voice startled Riezel awake.
"It's not just about inhaling a large amount of air, finding the right moments to inhale and exhale is also important, youngster!"
As that familiar booming voice echoed once again, Riezel was finally brought back to reality. Turning his head to the side, he discovered that someone had already taken a seat next to him.
It was the young man with the flame-patterned haori.
With a plethora of bento boxes in hand, the young man quietly sat beside Riezel, holding an open bento box, eating while flashing a wide smile at him.
"Keep it up, keep breathing! The state you were in just now was good. If you can maintain that kind of breathing state, you'll be ready in no time!"
It was evident that the young man had noticed Riezel mimicking his breathing. However, not only did he not mind, but he also offered guidance, appearing as if he were a mentor.
"Sorry..."
Riezel naturally wouldn't continue as if nothing had happened after being caught red-handed by the other party; he apologized, bowing his head slightly toward the young man.
"Your breathing is quite unique and interesting, so I unconsciously imitated it without asking. My bad."
However, the young man seemed unfazed, continuing to eat his bento.
"Delicious!"
After taking a bite, the young man immediately praised loudly.
Riezel soon noticed that the bento the young man was eating seemed to be from the same place as his.
"Delicious!"
Once again, the young man praised loudly before looking at Riezel.
"I'm Rengoku Kyoujurou! What is your name, youngster?"
Needless to say, the young man with the flame-patterned haori was none other than Rengoku Kyoujurou, the Flame Hashira of the Demon Slayer Corps, one of the most important characters in the Mugen Train Arc.