Isekai Adventure in the Dimensional Cube

"Dingling—"

It seemed like the sound of wind chimes could be heard.

Some distant, yet seemingly very close.

"Dingling—dingling—"

The rhythmic sound of the wind chimes seemed to awaken oneself, calling out enticingly and melodiously.

In a haze, Reiger followed the sound of the wind chimes, slowly walking towards a direction.

"Where is this...?"

When Reiger came to his senses, fully awake from his trance, he suddenly realized he had arrived in a completely unfamiliar place.

"The mountain top?"

Indeed, Reiger had reached the summit of a mountain.

It was apparently very high and close to the sky, completely bathed in sunlight, making the sun appear unusually large.

"How did I end up here?"

Reiger furrowed his brows.

Wasn't he on the Infinite Train?

One second ago he was having his ticket clipped by the conductor, and the next second, how did he end up here?

Could it be...

"Was I hypnotized? Is this a dream?"

Realizing this, Reiger was somewhat shocked.

With his highest level of "Abnormal Resistance" ability, immune to mental interferences, he had been hypnotized by a demon on the Infinite Train?

That couldn't be possible, right?

Yet, the reality before him told Reiger, whether he believed it or not, he had indeed entered a dream.

The evidence was that even though it was the high mountain top with strong winds and intense sunlight, Reiger couldn't feel a single breeze passing through his body, nor the warmth of the sunlight.

"Interesting."

Upon confirming this, Reiger murmured to himself, then suddenly reached out and grabbed his own neck, preparing to break it.

This was the most effective way to escape the demon's dream on the Infinite Train, by killing oneself in the dream, he could wake up.

However, just as Reiger was about to deal himself a deadly blow, a deep voice suddenly reached his ears.

"The Sun Breathing style has a total of thirteen sword forms."

As such a voice suddenly resounded, penetrating his ears, Reiger's motion to break his own neck paused.

It was only then that Reiger realized he was not the only one on this high mountain top.

Another figure had appeared there, appeared on the summit, facing away from Reiger, exuding an incredible aura all around.

This person had black hair tied into a high ponytail, the edges tinted red, and was clad in a red feather robe, holding a sword in hand as he stood against the sun in the sky, making the sun his backdrop.

"Dingling—"

The familiar sound of wind chimes rang again, emanating specifically from his ear area.

On his ears, he wore a pair of sunflower paper earrings.

Those earrings, were identical to the ones Tanjirou wore on his ears.

"You..."

Reiger stopped his actions and staring at the swordsman standing before him against the sun, was momentarily stunned.

"Inhale—exhale—"

The next second, the mysterious swordsman began breathing inexplicably.

The swordsman, drawing in a large amount of oxygen through his mouth, maintained his back-to-Reiger position, demonstrating a peculiar breathing technique before Reiger.

This breathing technique was somewhat similar to Kyoujurou's Flame Dance, yet distinctly different.

Kyoujurou's breathing was strong and powerful, each exhalation carrying a slight sensation of heat as if exhaling not air, but flames.

The mysterious swordsman's breath shared the powerful, fiery sensation of Kyoujurou's Flame Dance, each exhale also bringing a slight sensation of burning heat, but in contrast to Kyoujurou's Flame Dance, the swordsman's breath not only carried heat and destructive power but also a sense of endless life force.

The swordsman facing the direction of the sun had an even more incredible aura emanating from him, as if no longer a human, but transformed into a sprite.

Then, the sprite-like swordsman began to dance.

"Sun Breathing·First Form·Round Dance."

Accompanied by a low whisper, the swordsman released a slashing strike forward.

It was an arc-shaped slash.

The speed of the slash was rapid, appearing like a fleeting ray of sunshine at first glance, blazing into flames as it cut through the air, and ultimately drawing a sun-wheel trajectory, slicing through the void and the atmosphere.

"Sun Breathing·Second Form·Biluo Sky."

The swordsman's blade turned, linking the next strike very naturally and smoothly, leaping high, twisting his body, his sword aflame as he slashed downward from above, drawing another trajectory of a sun-wheel on the ground, causing flames to spread outwards into a fiery circle.

Wherever the fiery circle passed, everything was scorched by the flames, not only leaving blackened traces but also a startling cut-mark as if it could slice off the entire mountaintop, with an astonishing impact.

In this manner, the swordsman frequently danced and demonstrated his sword techniques.

"Blazing Sun Reflection."

"Phantom Sun Rainbow."

"Train."

"Bone-Burning Sun."

"Sun Spark Surge."

"Flying Wheel Yang Flame."

"Slanting Sun Turnabout."

"Radiant Grace Light."

"Sun Halo Dragon·Head Dance."

"Flame Dance."

Each movement was a sword form.

Each strike was a sword technique.

The Swordsman continuously practiced these twelve sword forms, facing the sun, his back to Reiger, wrapping his entire body in flames, dancing gracefully like a spirit of flame.

No, that's not right.

Not a spirit of flame, but a spirit of the sun.

Reiger was struck by an illusion that the swordsman had flown out from the sun he faced, even though flames fiercely roared around him and his blade seemed to cut through the air, cut through the earth, cut through everything, burning all existence, yet incredibly, it did not evoke fear but rather a profound closeness to nature and a mysterious enchantment.

It was not the flames that destroyed everything, but the light that drove away all evil.

It was not just the high temperature that could evaporate substances, but the sanctity that could purify demons and spirits.

"Inhale—exhale—"

As the Swordsman danced amidst roaring flames, he continuously executed fierce and powerful sword techniques while rhythmically breathing, a breath that was not very obvious yet echoed clearly in Reiger's ears, allowing Reiger to experience the subtlety of that breath in the most direct way.

Watching all this, feeling all this, Reiger unconsciously lowered his hand from his neck.

He was immersed in the Swordsman's sword dance.

He was deeply captivated by the sword forms practiced by the swordsman, unable to shift his gaze or remember anything else.

Each strike, each sword form wielded by the sun-like swordsman, was deeply ingrained in his mind, deeply embedded in his heart, unforgettable to him.

Gradually, Reiger even began to unconsciously mimic the marvelous breathing echoing in his ears.

"Inhale—exhale—"

Just as he had mimicked Rengoku Kyoujurou's breathing on the Infinite Train, Reiger started mimicking the Sun Swordsman's breathing.

Whether it was the frequency or the count, the extent, timing, volume, rhythm, and so forth of the breaths, Reiger instinctively moved closer to the sun-like swordsman.

"Thump-Thump—"

His heartbeat started to accelerate.

The flow of his blood also sped up.

His lungs expanded continuously, enabling Reiger to inhale more, bigger, fiercer oxygen.

If it had been under normal circumstances, Reiger might have been worried about oxygen poisoning due to the large amount of oxygen he was taking in. Only at this moment would he set aside all thoughts and focus wholeheartedly on breathing with the Sun Swordsman and immersing in the latter's sword dance, almost irresistibly.

Unnoticed by Reiger, as his breathing changed, the power emerging from within him also became stronger and more ferocious.

It was a strength that was incomparable to the power generated by imitating Rengoku Kyoujurou's Flame Breathing.

A style of breathing far more powerful than Flame Breathing, and far beyond the capabilities of current active Demon Slayer Corps swordsmen, appeared right before Reiger's eyes.

The Sun Swordsman seemed intent on passing this breathing technique to Reiger, repeatedly practicing, showing it without rest.

After hundreds of repetitions, the other party seemed to have an endless supply of energy, not tired, not weary, with his sword-holding hand not even shaking once, and the posture not deviating from the start to the end.

There was only one problem.

"Sun Breathing has thirteen forms."

Each time he practiced, the other party would mechanically state this fact.

Yet, from start to finish, the sword forms shown to Reiger had only been twelve.

"Round Dance," "Biluo Sky," "Blazing Sun Reflection," "Phantom Sun Rainbow," "Train," "Bone-Burning Sun," "Sun Spark Surge," "Flying Wheel Yang Flame," "Slanting Sun Turnabout," "Radiant Grace Light," "Sun Halo Dragon·Head Dance," "Flame Dance"—

The Swordsman showed only these twelve forms, never once practicing the thirteenth in hundreds of repetitions.

Yet he repeated the fact, telling Reiger that Sun Breathing comprised thirteen forms.

Why was that so?

Perhaps only Reiger, who was well-versed in the original story, would know why.

Just as Reiger's breathing and the Sun Swordsman's became entirely synchronized, and as the other's sword forms were completely etched into his mind and deeply embedded in his heart, the man finally stopped.

"... I leave it to you."

That was the last thing Reiger heard, a whisper that seemed almost absent.

"Tinkle—"

The earring of the Swordsman swayed again, ringing like a wind chime.

Reiger felt the scene before him fading, his own consciousness gradually distancing, slowly disappearing from this world.