Sukuna was somewhat surprised. He hadn't expected that a longsword made of flesh and blood could regenerate, let alone undergo this degree of transformation.
But facing Kokushibo's Sixth Form: Perpetual Night, Lonely Moon - Incessant, Sukuna felt no pressure at all. He calmly used Fourth Form: Burning Bones, Summer Sun and effortlessly neutralized the attack.
And while executing Fourth Form: Blooming Flame Undulation, he also severed the fully regenerated sword in Kokushibo's hand.
After cutting the Kyokokukamusari again, Sukuna observed exactly how it managed to restore itself.
After all, a sword built from flesh and blood should theoretically also be unable to regenerate easily due to the Red Blade's effect.
But this time, Sukuna saw it clearly. The sword wasn't regenerating. Rather, a new blade was rapidly growing from the hilt, creating the illusion of recovery. So the severed cross-section never mattered.
Kokushibo wasn't discouraged by this failed strike. On the contrary, the result only intensified his desire to defeat Sukuna and prove himself.
Seventh Form: Mirror of Misfortune - Moonlit
Eighth Form: Moon-Dragon Ringtail
Ninth Form: Waning Moonswaths
Kokushibo unleashed a relentless flurry of sword techniques at Sukuna. Compared to the completely unharmed Sukuna, the surrounding scenery wasn't so lucky—it had already been reduced to rubble under the barrage of techniques.
Even as the Kyokokukamusari was repeatedly severed, it didn't stop him from completing his techniques. Time and again, a fresh blade grew instantly before the next strike.
The continuous exchange allowed Sukuna to understand Kokushibo's situation. Simply put, he was a demon swordsman with physical abilities stronger than the Demon Slayer Corps' Hashira.
His attacks were nothing but sword techniques. That flesh-and-blood longsword in his hand was likely his Blood Demon Art.
Was Kokushibo strong?
He was indeed the strongest opponent Sukuna had encountered so far in this world. But boring was also the right word. No matter what sword technique Kokushibo used, it was still just a sword technique. It couldn't give Sukuna any more novelty.
Kokushibo's level of surprise was even lower than that of Nakime, who created this Infinity Castle.
Speak of the devil. Through her observation of the fight between Sukuna and Kokushibo, Nakime gradually grew able to follow Kokushibo's rhythm.
So Nakime began controlling the Infinity Castle's spatial architecture to provide some assistance whenever Kokushibo attacked Sukuna.
Even so, it didn't change the fact that Kokushibo couldn't touch Sukuna. But both Sukuna and Kokushibo were displeased by Nakime's meddling.
Sukuna found the mosquito annoying. Kokushibo resented the interruption of his battle.
But it didn't matter now. Sukuna had grown tired of playing.
Fourteenth Form: Catastrophe, Tenman Crescent Moon
Kokushibo gripped the sword tightly and unleashed a whirlwind-like torrent of consecutive slashes at Sukuna.
But Kokushibo, seeing Sukuna so clearly through the Transparent World, watched as Sukuna simply raised his Nichirin Blade and pointed it at him. Kokushibo didn't yet understand what that meant. In the next instant, something instantly split apart the vortex he had created.
"What?"
Both his sword technique and the sword itself were severed in that instant by an invisible slash. His head was severed along with them.
Kokushibo's rolling head saw the still-composed Sukuna and felt overwhelming resentment.
He had already resolved himself. He would never lose to anyone again...
Even now, decapitated, he refused to lose a second time...
Under Sukuna's very gaze, blades identical to the Kyokokukamusari sprouted from all over Kokushibo's body. And from the clean cross-section of his neck, a new head rapidly grew. But compared to his original human head, the newly grown head was completely aberrant—the very embodiment of a demon.
But the moment Kokushibo regained his vision, all he saw was a ferocious flame tiger roaring down upon him. Only when he looked through the Transparent World did he fully realize—it wasn't a flame tiger at all, but a Nichirin Blade, its blade crimson, radiating terrifying "fire" as it hurtled toward him.
The savage flame tiger collided with Kokushibo, effortlessly tearing away his entire upper body.
With the Red Blade's enhancement, such a severe injury already spelled Kokushibo's death.
And Sukuna? He remained standing in his original spot, having not moved an inch.
That final flame tiger attack was merely Sukuna throwing his Nichirin Blade—a declaration that he was done playing swordsman games.
If Kyojuro Rengoku's explosive power had once caught Sukuna's interest, after seeing so many swordsmen and demons, even Kokushibo—the strongest among them—only inspired boredom in Sukuna now.
Because his strength was merely "strong" by this world's standards for demons and humans. Not the kind of strength that could threaten Sukuna. So it had no impact on Sukuna's judgment whatsoever.
This consecutive battle left only awe in the hearts of the surviving Hashira like Shinobu, watching from afar.
Though the distance was too great for them to see the fight's details or identify which Twelve Kizuki Sukuna was facing—or even if they were Twelve Kizuki at all—they could clearly see the large-scale attacks unleashed by Doma and Kokushibo. Shinobu couldn't even imagine whether their remaining Hashira could win against demons of that level...
But against enemies of that caliber, Sukuna had casually dispatched both within minutes.
Sukuna stroked his chin and muttered to himself. "What now? Should I just destroy this space directly..."
But he quickly dismissed the idea. Destroying the space would quickly eliminate every living thing inside, including Muzan. But such an execution would lack substance. It would feel like a shame if that bastard Muzan didn't die miserably right before his eyes.
Just as Sukuna was pondering, a figure appeared not far behind him as the Infinity Castle shifted.
Sukuna turned to look. He saw a woman in a kimono. But anyone appearing here was most likely a demon. He had already killed most of the Upper Ranks. So he guessed that the demon daring to appear before him now was likely the one controlling this space.
But Sukuna quickly caught a familiar scent.
"Hm? No, you are..."