As it stood, the demon before them had speed and strength that far exceeded both Takeo and the demon slayer.
On top of that, it had terrifying regeneration and a Blood Demon Art that functioned like a supernatural ability.
It was clear this enemy was not someone the two of them could handle alone.
Takeo had a bit of hand-to-hand combat skill and a weak regenerative ability—barely enough to be called special in front of this fucker's healing.
The demon slayer had training and a Breathing Technique, but even so, his overall strength was still below that of the water demon.
The only thing between the two of them that posed a real threat to the demon…was the demon slayer's Nichirin sword.
And yet, the slayer hadn't been able to land a clean hit to the neck.
"What's wrong? Done attacking already? In that case…" the water demon said, voice twisted with irritation. He flexed his recently reattached right arm, then suddenly swung it toward the floor, his expression contorting into a snarl.
"…Let me take a turn, then!"
Fwoosh—!
Countless droplets of water lifted from the floor, and in the blink of an eye, they sharpened into needle-like spikes, hurtling toward the two of them in a dense barrage.
There was no time to think. Both Takeo and the demon slayer immediately leapt into motion, dodging while simultaneously swinging their blades to deflect the incoming spikes.
Clang! Clang! Clang!
They rang out like metal against steel.
Despite being made of liquid, the spikes struck with the hardness and sound of forged blades!
Takeo's sword was dented in an instant, battered by the barrage of water spikes. A few even struck his body, cutting through his clothes and drawing blood.
He turned to check on the demon slayer.
Although the slayer had also been hit, his uniform had absorbed the impact. The thin water spikes weren't able to pierce it. That black outfit, resembling a military uniform, had shockingly high defensive capabilities.
…What kind of futuristic gear is this?
Takeo couldn't help but envy the slayer's equipment, but he also knew that even with it, it wasn't enough to fully protect against the water demon.
The wounds on the slayer's body made that much clear—the demon still had ways of bypassing the uniform's defense.
Dodging the flurry of spikes, the slayer once again lunged at the demon, Nichirin blade swinging.
Takeo tightened his grip on his sword and followed close behind, but his eyes darted side to side as he moved—searching for anything useful.
After all, what separates humans from beasts is their ability to use tools.
If he couldn't overpower the demon directly, then why not look for a tool that could?
They were in a cargo hold, after all. Among the goods being transported by the merchant Miura Tarō, there were plenty of things beyond just porcelain.
Could something in here be used against a demon?
Takeo's mind was racing as he fought, coordinating attacks alongside the demon slayer.
Despite it being their first time meeting—let alone fighting side by side—their teamwork was surprisingly fluid. At a glance, it even looked like they were evenly matched against the water demon.
But both of them knew that was an illusion.
The only reason they were keeping up was because the demon was deliberately avoiding close combat—refusing to engage directly with the slayer's sword.
It clearly understood that the Nichirin blade posed a real threat. Instead, it relied on its Blood Demon Art to keep them both at bay with long-range pressure.
This wouldn't last.
Human stamina couldn't compare to that of demons. Even Takeo, with his enhanced endurance, couldn't keep up indefinitely.
If this dragged on any longer, they'd both die here.
"Hey!" Takeo called out through gritted teeth, frustrated that he hadn't found a useful tool. He turned to the demon slayer. "That technique you used earlier—when your blade was wrapped in wind—what was that?!"
"That's… a Breathing Technique. Why are you asking about that now?"
The demon slayer replied quickly, still keeping his eyes locked on the enemy.
"Yes, that's it! Teach me!" Takeo shouted back, now standing shoulder to shoulder with the slayer, his tone resolute.
"...What?"
The demon slayer froze, staring at Takeo like he'd just said something insane."Are you out of your mind? Do you have any idea how difficult it is to learn Breathing Techniques?!"
"I don't!" Takeo shot back immediately. "But do we have any other way to get stronger right now?!"
He didn't know how hard it actually was to learn a Breathing Style. But with his enhanced body and Wolverine's combat instincts, he figured his learning curve would be way faster than the average person's.
There was a massive difference between someone who had never trained and someone who had years of combat experience.
And right now, if there was any hope of boosting his power quickly, it was through the Breathing Technique the slayer had just used—it was his only shot.
At this point, the situation was already desperate. No matter how impossible it sounded, he had to try.
The demon slayer was silent for a moment.
…Takeo wasn't wrong.
Aside from teaching him Breathing, there was no other way left to increase their chances of survival.
It was still hours until dawn. They were at sea. There wasn't a single other person on board capable of fighting a demon .Just this boy—this strange, persistent boy who refused to back down.
There was no choice. Even if it was like treating a dying horse with medicine, the demon slayer had to try. He had to teach Takeo the basics of a Breathing Technique.
"…Listen carefully. The Breathing Style I use is called Wind Breathing. It has a total of nine forms. The breathing technique itself is—"
The demon slayer spoke rapidly, quickly explaining the fundamentals of the technique he had learned.
But before he could finish, the water demon's attacks came crashing down once more.
Like a predator toying with its prey, the demon conjured a barrage of fine water needles, launching wave after wave of densely packed strikes that were nearly impossible to dodge.
In such conditions, Takeo's wounds continued to multiply. The demon slayer, though not visibly injured thanks to his uniform, was clearly struggling too—Takeo could hear his breathing grow heavier, his stamina depleting fast.
Despite the onslaught, the slayer continued to explain—albeit in broken intervals—the principles and training methods behind Breathing Techniques.
According to him, the core of a Breathing Style lay in enhancing the heart and lungs, enabling the blood to absorb oxygen in massive quantities instantly.
This, in turn, would amplify the body's physical capabilities across the board—strength, speed, endurance—bringing a demon slayer to the level needed to contend with a demon.
That was the foundation upon which the Demon Slayer Corps stood. Without it, no human could hope to fight demons on equal ground.
All Breathing Styles originated from the Basic Breathing Technique, which served as the root.
Currently, the Corps trained its swordsmen in five major styles: Flame, Water, Wind, Thunder, and Stone.
Every new member of the Corps began by learning one of these fundamental styles.
Only by mastering it and surviving the Final Selection could one become an official demon slayer.
Beyond the foundational Breathing Styles, there were rare individuals—geniuses—who could use those core styles as a base to create entirely new, personalized Breathing Techniques.
But those were exceptions, and the demon slayer didn't go into that.
The style he used was Wind Breathing, characterized by its speed and sharpness. When wielded properly, Wind Breathing could generate slicing gusts capable of cutting down enemies or entangling them in currents of wind to restrict movement.
Although the demon slayer had trained in Wind Breathing, he hadn't mastered all of its forms. His strongest werethe Second Form and the Fifth Form, and so those were the only two he passed on to Takeo.
Learning a Breathing Technique in the middle of battle was supposed to be impossible.
But even knowing that, the slayer still taught Takeo everything he could—just in case.
Talking during battle disrupted his own breathing rhythm, and he had already been fighting the water demon for a long time. His stamina was nearing its limit.
So it was no surprise when, during one of his attacks, the slayer finally slipped up.
The demon spotted the opening—and slammed a vicious kick straight into the slayer's gut.
Boom!!
"Shit! Ugh—!" The demon slayer's body shot back like a cannonball, crashing into a stack of nearby crates.
Crash!—clang—thud!
Wood and cargo scattered in every direction.He lay there, sprawled in the wreckage, trying to get back up… but in the end, he couldn't.
In contrast, the water demon, though covered in wounds, had already healed completely.
Its stamina seemed slightly drained, but its overall condition was solid—like it could keep fighting for a long time still.
"Well, well, what's the matter? Done already? I was so scared of you demon slayers I ran all the way up to this ship… and this is all you've got?"
Having taken down the demon slayer, the demon began taunting them with arrogant bravado.
Its long tongue licked across its lips, and its eyes gleamed with hunger—the kind that only came from craving flesh.
Seeing that the demon slayer couldn't get back up, the demon tilted its head and turned to look at Takeo, who was still gripping his sword tightly.
"Hey, kid. He's finished. You really planning to keep fighting? Tell you what—why don't you do me a favor and finish him off for me? If you do, I'll let you and that little brat over there go. You don't look like you've got much meat on you anyway…"
Maybe it was because Takeo looked thin and less appetizing than the demon slayer, but the demon seemed willing to let him live.
Takeo said nothing.
He's lying. That demon… he said he'd let them go.
But he won't.
Takeo could see it in the demon's eyes. There was no mercy there. Only hunger and anger for the previous wounds that Takeo had given him.
So this.. this is the fear... of death.
This wasn't just some random fight.
This is his second chance.
He used to be just another face in the crowd. Another nobody.
But somehow—by some miracle—he'd gotten a new life. A stronger body. A cheat code.
So what if learning a Breathing Technique in a few minutes is supposed to be impossible?
If he doesn't learn it now, he dies.
That's it. That's the truth.
So really, there is no choice.
No second thoughts. No hesitation.
I have to do this. I will do this.
Inhale. Exhale. Inhale. Exhale…
The cold air inside the cargo hold flowed through his windpipe, down into his lungs, and spread through his entire body.
Following the instructions the demon slayer had given him, Takeo was trying to grasp the foundation of this world's power—the path of the Breathing Technique.
Seeing that Takeo wasn't responding, the water demon lost its patience.
The Nichirin sword capable of harming him wasn't in Takeo's hands—there was no longer any need for caution.
Lowering his body, baring his fangs, the demon snarled:
"Not gonna answer?"
Inhale—
Exhale—
He could feel the wind—feel it running through his lungs, coiling inside his chest, surging into his limbs.
Something was awakening.
Something sharp. Fierce.
"…Then die!!"
Boom!
In an instant, the demon's body vanished from where it stood.
Whipping its long, serpentine water-tail behind it, the demon moved faster than the eye could follow. In the blink of an eye, it had already closed the distance—appearing right in front of Takeo!
The demon slayer, still collapsed in the wreckage of broken crates, saw what was happening. He struggled with everything he had to stand, but his body wouldn't respond.
All he could do was watch—eyes wide—as the demon's claws tore through the air, ready to rip apart the red-haired boy before him.
But—
Just as the attack was about to land...
Wind stirred inside the cargo hold.
His animal-like instincts roared!
I refuse to die here.
Not now. Not like this.
Invisible currents coiled around Takeo's blade, and in the next breath, with the force of the wind behind him—Takeo brought the sword crashing down toward the demon's head.
Slash! Slash! Slash! Slash!
Four slashing wind blades tore through the water demon's body like claws.
Four deep wounds split open across its torso, and a torrent of blood burst forth—spattering across the floor and mixing with the water pooled beneath them.
"Th-That's—!"
The demon slayer's eyes went wide—wider than they had the entire fight.
As a practitioner of Wind Breathing, no one understood what had just happened better than he did.
What Takeo had just unleashed… was unmistakably Wind Breathing!
The very technique he had just taught him—
Wind Breathing, Second Form: Claw-Purifying Wind!