"BOOM!!"
Thunderous roars of battle echoed endlessly within the Infinity Castle.
Meanwhile, in another location, Kokushibo—with his six eyes and marked forehead—stood calmly amidst a set of folding screens, silently awaiting the developments.
"Doma's presence has vanished? And… that new Upper Rank Six as well?" Kokushibo muttered in mild displeasure. "Truly… useless trash."
"And this sound now… is that Akaza?" Kokushibo focused his senses on the spiritual presences within the Infinity Castle. He could clearly identify that the source of the booming battle was indeed Akaza, locked in fierce combat.
"His aura has grown even stronger. Has he neared that ultimate realm…?" Kokushibo mused. "But could someone from the Demon Slayer Corps really be capable of battling Akaza to this extent…?"
He had no knowledge of the specific situation Akaza was facing. At that very moment, deep in the poisoned blood-soaked region of the castle, Kairo Retsu was locked in brutal combat with Akaza.
Each of Akaza's punches cut through the air with a piercing whistle, and whenever his blows landed on Kairo Retsu, the impact would ring with a shrill resonance.
If any regular member of the Demon Slayer Corps were to witness this scene, they would instantly recognize—
Akaza's attacks were far beyond what any normal human body could withstand.
Yet Kairo Retsu—
Through sheerly enhanced defense and the resilience granted by his Hunter's equipment, was holding his own against Akaza. Time and again, he even landed counterblows by trading injuries.
In this battlefield soaked with wisteria-laced blood, the two—both unafraid of injury—repeated the cycle of wounds and recovery over and over.
Akaza began to realize: though the man in front of him could recover from injuries, he… still clearly felt the pain.
"You…"
After once more shattering the bones in Kairo Retsu's arm as he blocked a blow, Akaza took a few steps back, standing knee-deep in poisonous blood, and said:
"That regeneration—doesn't belong to you, does it?"
"Tch…" Kairo flexed his arm as it reformed, scratching his head. "Was it that obvious?"
"If you were a demon, you'd have already acclimated to the sensation of injury." Akaza pointed at him. "You, self-proclaimed 'Hunter'—not only have you never fought before, you haven't even adapted to pain. Just what are you?"
"Couldn't have said it better myself." Kairo gave a big thumbs-up. "You're real sharp, huh? Truth is—half a month ago, I wasn't even a Hunter. Fighting? Never did it… Oh! My most intense brawl was in middle school—when I gave someone a lump on the forehead!"
As he said this, Kairo rolled his neck and shook out the residual stiffness in his limbs from their battle.
"So why waste your breath?"
Kairo faced Akaza and said bluntly:
"To send you to Hell fair and square… Even a guy like me—someone who barely ever fought—is stepping onto the field."
Striking a strange pose, Kairo declared:
"I believe in pragmatism. If something leads to the best outcome, and everyone's on board—then I'll do anything to get it done."
"Akaza," Kairo said, beckoning with a crooked finger, "if you remembered your human memories, you'd have taken your own life in shame by now."
"But seeing as you haven't regained them, who knows what will happen… That's why—" Kairo guided his Kinsect through the air, "—I'll personally accompany you. Whether you remember or not, the best resolution awaits—redemption in Hell."
"Maybe once you're down there, you'll even thank me," Kairo said with a grinning, cheeky tone.
"You've lost your mind!" Akaza's veins bulged in rage. "Why would I take my own life?!"
His anger flaring, Akaza dropped into a combat stance.
"I should be thanking you for the pressure you and your comrades gave me! That sensation… it's finally within reach!"
"The ultimate domain I've pursued for centuries—I can feel its edge!"
"Just one blow to your brain—if I crush your head, there's no way you'll regenerate."
"After I kill you, I'll hunt the others down, one by one. I'll keep fighting. I'll grow stronger. I'll reach that ultimate realm. And then—!"
"Wow, you really are amazing." Clap clap clap, Kairo applauded mockingly. "Enough talking. Let's get to it."
Kairo tapped his own forehead. "Right here. My brain. Make sure it's a one-shot kill, or else… I'll be a real pain to deal with."
The very next moment, Akaza moved—and Kairo Retsu, prioritizing the safety of his own head, countered as best he could.
Meanwhile, Joseph Joestar, Kazuma, and the others were already setting their plan in motion.
"My Blood Demon Art can influence others via the scent of blood," Tamayo explained, "but this is my first time attempting to liberate someone's full physical potential through a scent."
Her technique now radiated toward everyone present.
"This will place a massive strain on your bodies—but thanks to the special healing abilities the Hunters brought, you should recover quickly," Tamayo said. "However, the enhanced physical strength—you'll have to handle that yourselves."
"This power… is incredible!" Inosuke bellowed, twin blades raised high, veins bulging all over his muscular form.
"My heart rate… is so fast," Giyu murmured, gripping his Nichirin Blade. "With this… I can fight him."
"That's why we told you. That red blade thing is just grip strength—it's up to you to figure it out," Kazuma muttered with frustration. "Can't believe I'm the one who has to take this risk…"
"What's the problem? You've got me backing you up!" Joseph slapped Kazuma firmly on the back. "Besides, you're a comedy protagonist, right?"
"Shut up, you oversized muscle-head!!" Kazuma yelled in embarrassment. "I refuse to admit I'm the MC of a comedy anime!!!!"
"Anyway, you all understand by now, right?"
Joseph, using his towering height to gaze down at the Demon Slayer Corps members, declared:
"The plan is to use one life… to drag Akaza down to Hell."
"But the one paying the price…" Tanjiro said, concern in his eyes, glancing in a certain direction.
At that moment, Kairo Retsu, still locked in combat with Akaza—
Grinned brilliantly.
"Come on then! Let me find out… just where the Cart sends a Hunter!!!"