Night had fallen, and a pale moon hung high in the sky, casting its silvery glow over what should have been pitch-black mountains.
In the depths of this forest, a white-clad figure darted swiftly among the trees. His face was a mask of terror, and he kept glancing behind him as if a grim reaper were relentlessly pursuing him.
After a brief look back, he turned forward again—but this time, the fear in his eyes deepened.
On the trunk of a large tree not far ahead, a figure had silently appeared. The boy looked barely twenty, his youthful face almost innocent, yet his crimson eyes, patterned with unusual black markings, glowed menacingly under the moonlight.
In his hand, he held a long blade emanating an icy aura, a silent announcement of death.
That boy was Karasuma Reiyu, who had already spent two years in this world.
Reiyu stood high on the tree, looking down at the figure that had been fleeing in panic. A faint, almost imperceptible smirk lingered in his gaze.
The "figure" below wasn't human—it was a demon, one of the creatures unique to the Demon Slayer world. They moved only at night and could never endure sunlight.
"Why'd you stop running?" Reiyu taunted, his voice dripping with mockery.
"Damn demon slayer…"
The demon, realizing escape was impossible, hesitated a moment before baring sharp claws and lunging at Reiyu.
Its speed would have seemed impressive to any normal human, but to Reiyu, it crawled like a snail. With his Mangekyou Sharingan, he could slow down opponents, easily spotting openings to counterattack. Even without using it, the sheer gap in their strength made the demon sluggish in Reiyu's eyes.
With a casual sidestep, Reiyu evaded the attack. Having already turned the encounter into a playful chase, he had no interest in prolonging it.
He raised his long blade. A white flash of light cut through the night, and the demon's head was severed without mercy.
Demons in this world weren't like humans. While sunlight was lethal, ordinary weapons had almost no effect. The only sure way to kill one was to decapitate it and crush the head into paste—a slow, arduous process.
Eventually, demon slayers discovered Nichirin Blades, swords forged from sunlight-absorbing ore. A single strike to the neck could guarantee a demon's permanent death. Along with specialized breathing techniques, these color-changing swords became the ultimate tools for hunting demons.
Reiyu wielded an unused Nichirin Blade given to him by Urokodaki Sakonji. His unique Devouring Breathing was a completely original technique, not derived from any known breathing style, causing his blade to glow black—a rare sight in the Demon Slayer world.
As the demon's body dissolved into ashes, a barely perceptible transparent glow was absorbed into Reiyu's blade.
Ding!
"Congratulations, Host! You have killed and devoured a low-level demon. Combat power increased by 3 points."
"Total Combat Power: 372 points.""Overall Rating: Level 3."
This was the essence of Devouring Breathing—even if Reiyu killed a demon without using sword techniques, he could absorb its energy to boost his own power.
The past two years had been grueling. For a year and a half, Reiyu had undergone relentless training under Urokodaki on Sagiri Mountain. Thinking back, he still shivered under the old man's strict control.
Urokodaki, former Water Hashira and current demon-slaying mentor, had trained him in Water Breathing. Strangely, Reiyu never learned it properly. Instead, during his Water Breathing training, he had discovered Devouring Breathing.
Though surprising, Urokodaki assumed it was merely a branch of Water Breathing. And the only reasonable explanation for such a rookie inventing a new style? A genius.
Six months after Sagiri Mountain training ended, Reiyu officially became a demon slayer. He had raised his pitiful -5 combat power to 372 points, elevating his rating from infuriating Negative Level 2 to Level 3.
To reach Earth Level, he would need 800 points—a long road ahead, since demons weren't easy to find.
Now, Reiyu was headed to a place teeming with low-level demons: Fujikasane Mountain, the official site of the Demon Slayer Corps' final selection.
This was the proving ground where recruits earned their rank as full-fledged demon slayers—a place designed to test every skill they had learned under mentors like Urokodaki Sakonji.
Though he had a junior disciple arriving a few days after him, Reiyu chose to head to Fujikasane Mountain ahead of schedule.
The hunt, the thrill, and the opportunity to devour countless demons—these were his true motivations. Becoming an official demon slayer was just a convenient bonus.