"Kill you! Kill you! Kill you! Kill you!"
The demon clawed frantically at its own head, muttering under its breath in a crazed loop. Bloodshot eyes, erratic movements—it looked utterly unhinged.
Shirou felt no sympathy for a creature like this. He certainly wasn't going to just stand there watching it unravel like some grotesque performance art. His goal was singular: defeat it by any means necessary.
Even if he couldn't kill it, escaping this place was still possible. But… perhaps it was possible to kill it.
The blade in that boy's hand—that was the key. It seemed to slow down the demon's regeneration.
"[Wind Breathing—First Form: Dust Whirlwind Cutter]!"
A powerful shockwave exploded outward as the boy surged forward like a bullet, his body spinning in a spiraling wind vortex that tore through the earth as it raced toward the demon.
"Not good!"
"Tch—"
The oni jerked its head back and retreated a half-step. The blade, glowing a brilliant green, just barely grazed its neck—leaving behind only a thin, bloody line.
The boy was already injured, and wielding the sword with his non-dominant left hand made the Wind Breathing technique far weaker than it should've been. The loss of an arm had thrown off his balance entirely. His precision suffered, and the strike didn't land clean.
"You really think I didn't see your little stunt?"
The demon, having dodged the blow, showed no mercy. It lashed out with one clawed hand, plunging straight through the boy's shoulder and hoisting him into the air like a broken doll.
There were only three people in this entire battleground, and aside from the sounds of clashing blades and footfalls, there was nothing to mask anyone's movements.
Even Shirou had noticed the boy reaching for his weapon—how could the demon, with its heightened senses, not?
The howl of the wind came next. A silver blade flashed across the oni's field of vision—another arm, freshly regenerated, was severed once again.
As it turned out, Shirou hadn't been idle during the boy's charge. He'd timed his approach with the gusts of wind stirred by the attack, sprinting full speed toward the demon's blind side.
Shirou couldn't teleport or use anything fancy—he just relied on his own two legs, pushing them as fast as they would go.
He wasn't some helpless civilian. And the demon wasn't so far above him that he'd just stand there watching someone die.
"You're seriously pissing me off!"
Within a few short breaths, the demon's arm began to regenerate once more.
Without Breathing Styles or a Nichirin Blade, Shirou didn't pose a lethal threat. The demon had instinctively ignored him in favor of finishing the boy off.
Even if it had been hellbent on killing Shirou just moments ago.
After all, Shirou couldn't kill it. Not really. With its regeneration, it could outlast him.
But the boy was different. If that blade hit its neck… it might actually die.
"I need to kill one of them first."
Even a wounded opponent could be a threat. And now there was this red-haired idiot from who-knows-where getting in the way.
One-on-two? The advantage still belonged to the demon.
Fueled by instinct, it exploded forward, diving toward its severed hand—the one still gripping the sword.
It hadn't received much of that person's blood and hadn't awakened any Kekkijutsu (Blood Demon Arts). That's why it had honed its swordsmanship so obsessively, slaying humans across the countryside in hopes of gaining that demon's favor.
It was an ambitious oni. Never one to fear death. Always seeking power.
"You alright?"
Shirou caught the boy just as he collapsed, barely managing to keep him from hitting the ground.
"Cough—Use this Nichirin Blade... cut off its neck. That'll kill it."
The boy, pale from blood loss, half-knelt on the ground as he passed the blade to Shirou, his voice weak but firm.
"Don't worry about me. This kind of wound won't kill me. Its power isn't strong enough to counter the Nichirin Blade."
Nichirin Blades were forged from ores that had absorbed sunlight, giving them a trace of solar energy—deadly to demons. Most demons would fall to a single clean cut from one of these blades.
Even without Breathing Techniques.
Breathing Styles were like the Hamon of this world—channeling a similar solar force through the user's body. Wind, Flame, Water—all were branches that traced back to the original Sun Breathing. Their strength came from a common source.
The combination of a Breathing Style and a Nichirin Blade allowed Demon Slayers to bring out the sword's full potential—to strike down demons with ease.
"Maybe... maybe I really don't have what it takes to be part of the Demon Slayer Corps."
The boy knelt there, lips curled in a bitter smile as blood trickled from the corner of his mouth.
He had trained under his teacher for years, but in the end, hadn't learned many techniques. His mastery of Breathing was far behind his peers.
During Final Selection on Fujikasane Mountain, he'd only fought weaker demons—hadn't even survived on his own. If it weren't for his senpai stepping in...
He would've died there.
Especially when he saw it—that monster that slaughtered other candidates like weeds in a field.
That was the first time he'd witnessed a demon with a Blood Demon Art. He had frozen in fear, body trembling uncontrollably. Couldn't move. Could barely breathe.
If that demon hadn't completely ignored him, he'd have become just another corpse feeding its strength.
As a member of the Corps, one was expected to be brave. After all, they'd slain countless demons. Without overwhelming odds, they shouldn't know fear—shouldn't feel despair.
But he knew his own limits.
He was only strong enough to pick off demons that lacked any Kekkijutsu.
What he hadn't expected... was that even one of those could be this strong.