Infinity Castle, Throne.
It was located at the deepest part of the Infinity Castle, perched atop the peak of a cliff-like massive structure.
It was extremely vast and spacious that it was difficult to see the edges at a glance, giving the impression of having reached the world's end.
Only a solitary throne stood there, exuding regal majesty.
Muzan sat on it, eyes closed, as if in a light slumber.
Until a moment when he suddenly opened his eyes, pupils akin to a serpent's, fixed forward, radiating an intense coldness.
It was indifference that symbolized his aloofness.
It was indifference that symbolized his ruthlessness.
To anyone who saw his cold eyes, it was immediately clear—this man, though appearing human in form, was undeniably a monster apart from humanity.
Such a monster now awaited another monster's arrival.
"Come?"
Muzan remarked coldly.
"Faster than I expected... It seems Nakime has indeed been held up by those pesky Hashira."
*Step!*
In response to his remark came the sound of footsteps.
*Step!* *Step!* *Step!* *Step!*
Unabashedly approaching the throne, came powerful and resolute footsteps.
Riezel advanced step by step toward the throne, gazing at Muzan seated upon it, without hesitation drawing his sword.
*BOOM!*
Flames engulfed, crashing upon the throne and shattering it into fragments.
Yet, in the split second before Riezel drew his sword, Muzan had already left the throne, leaping up and landing before him.
Muzan's demeanor remained indifferent as if no longer governed by emotion, sneering at Riezel.
"What's this for? Unwilling to hear someone speak above you? Or perhaps you don't want to look up at me from below?"
Riezel did not reply to Muzan's words, just calmly sheathing his sword.
At the same time, by Riezel's side, Tamayo appeared with Yushirou.
"Kibutsuji... MUZAN!"
Seeing her sworn enemy, whom she had dreamed of killing, Tamayo could no longer maintain her former elegance as her expression turned slightly ferocious and filled with hatred.
"So it's you, after all... Tamayo..."
Muzan turned his gaze toward Tamayo, his face taking on a slightly ferocious expression.
"I knew you wouldn't miss this opportunity, you damn traitor!"
"I've waited for this day for centuries, Muzan!" Tamayo shouted with anger. "For hundreds of years, I have fantasized about this day arriving! Now, your end has finally come, you damned monster!"
"If I'm a monster, then you're no different..."
Muzan shook his head, regaining his composure.
"I really don't get it... You were the one who killed your own husband and children, yet you come seeking revenge from me? It just doesn't make any sense."
With that, Muzan turned to Riezel, ignoring Tamayo's anger.
"And of course, the Demon Slayer Corps too... Everyone's out for revenge against me, ready to throw away their precious lives for it. I really can't understand such foolishness."
"Why throw away your life for the sake of avenging others?"
"What exactly do they think life is?"
For someone like Muzan, his own survival was always the most important thing.
As long as he could live, he would spare no sacrifice.
He cherished his life and loved his life greatly, but only his own. He could never understand why members of the Demon Slayer Corps would be willing to sacrifice themselves for those who had already died and been eaten by demons.
Because they were close relatives?
Because they were family?
So what?
All of those dead people were dead—once dead, everything was gone.
In that case, why not be thankful that they were still alive, embrace this luck, and live on forever, instead of seeking revenge on him?
Just because those people died because of him?
However, what did that signify?
"In this world, accidents happen all the time. Sometimes, natural disasters strike and can kill thousands in an instant. Even so, do humans ever seek revenge on them?"
Muzan pondered aloud.
"Not only has my life lasted longer than any natural disaster, but those I've killed are no different from those who perish in natural disasters. Given this, why do they seek revenge on me?"
"Especially those Ubuyashikis... they keep chasing me and even formed this so-called Demon Slayer Corps, which is nothing more than a group of lunatics, like an evil cult."
"Of course, you too."
Muzan pointed at Riezel.
"I don't know where you learned Sun Breathing or why you claim to be Tsugikuni Yoriichi, but from what I can tell, it seems you haven't lost any family or friends to demons."
"I couldn't even investigate your background and past—you seem to have sprung out of nowhere. I can't find anyone, whether family or friend, connected to you."
"Why would someone like you help those lunatics from the Demon Slayer Corps to kill me for no reason?"
"It makes no sense!"
Each word and statement from Muzan filled Tamayo's mind with rage, nearly driving her to lose control.
However, just as Tamayo was about to rush forward, Riezel reached out his hand and stopped her.
"It's true... When you think about it, I don't hold a grudge against you or your kind."
As Riezel said this with an indifferent tone, it caused Tamayo to look at him with incredulity while Muzan paused before finally smiling.
"That's right, we have no grudge against each other. We don't need to fight to the death like this."
Rarely offering advice, Muzan spoke in an advising tone to Riezel.
"Why bother with mere humans and those lunatics? With your power, you could become an immortal and noble being like me."
"I can give you half of my blood, making you a Demon King equal to me. Once I create a drug from the Blue Spider Lily that can overcome sunlight, we can share it and become perfect beings, immortal together."
"Don't think of me as a tyrant who doesn't let others exist on the same level as me. What I've always wanted is a perfect life, to be immortal. As long as that wish can be fulfilled, nothing else matters to me."
What Muzan said was indeed true.
All this time, he had only desired immortality, to become a perfect being. Whether there was another like him in this world was something he could choose to ignore.
As a result—
"Come, join me in becoming the perfect being, the perfect demon. Whether it's day or night, we will rule over all."
Muzan extended his hand toward Riezel, his tone filled with a seductive allure.
"Your Excellency!"
Tamayo immediately became anxious.
However, she didn't notice that Riezel's expression remained calm throughout, unaffected by Muzan's infuriatingly innocent declarations or his logically persuasive attempts.
"It seems you've misunderstood something here, Muzan..."
Riezel shook his head lightly.
"Sure, I have no personal grudge against you, but there are plenty of people you have no grudge against who were killed by you, aren't there?"
Upon hearing this, Muzan's smile froze.
"You've killed many people—some you consumed as food, some you killed because they were threats, and others just because they annoyed you. How many have died simply because you acted on impulse or were in a bad mood?"
"When you killed those people, was it because they had harmed your loved ones?"
"Weren't those people innocent victims too?"
"Yet, you killed them without reason, just like you said—it makes no sense."
Riezel raised his gaze, fixing it upon Muzan's eyes.
"If that's the case, why do I need a personal grudge against you to want to kill you?"
"Can't I just see you as food to make myself stronger and want to kill you?"
"Can't I just see you as a threat and decide to kill you?"
"Or maybe... I just find you annoying, so I act on impulse and want to kill you?"
"Compared to your logic, doesn't this actually make more sense?"
Riezel's half-mocking reasoning caused Muzan's face to darken, veins started to bulge on his forehead.
Despite this, Riezel continued.
"In your opinion, it might seem pointless and foolish for the Demon Slayer Corps to seek revenge on you since you see yourself as a natural disaster. But to me, calling yourself a natural disaster is just as foolish."
"You're right, humans don't seek revenge against natural disasters because no one believes they can actually defeat them."
"But you? Surely, you don't really think of yourself as terrifying and invincible like a natural disaster?"
With his voice turning cold, Riezel calmly looked at Muzan, whose forehead veins were bulging.
"You're nothing more than a rat that can only exist in the darkness. Compared to the Ubuyashiki family, you're just an undead who has managed to survive for centuries."
"No one sees you as invincible. Even if you're powerful, humanity still sees hope in killing you, as Tsugikuni Yoriichi's appearance proves."
"In the presence of absolute strength, you only qualify to flee in embarrassment."
"Yet, you dare compare yourself to a natural disaster?"
"How ridiculous!"
*WHOOSH!*
As Riezel's voice fell, a whip-like bladed flesh suddenly slashed through the air, crashing heavily toward him.
*BOOOM!*
Accompanied by a thunderous sound, the ground shattered under the impact of the whip, sending countless shards and debris flying, turning Riezel's position into a deep hole.
Luckily, Riezel, holding Tamayo and Yushirou, lightly floated back, evading the attack.
Muzan retracted his whip, his entire appearance transforming.
His hair turned white, his clothes vanished, and his body was covered in swamp-like darkness, with mouths growing on various parts of his body. From his back, thin, tendril-like whips emerged and flailed wildly.
On his face, a ferocious expression emerged.
"IF YOU WANT TO KILL ME, THEN COME AND TRY!"
Like an enraged beast, Muzan roared loudly.
"No need for you to tell me twice."
Riezel replied casually before dropping Tamayo and Yushirou, his eyes blazing with murderous intent.
At the same time, several Kasugai Crows circled in the sky, observing and relaying the current unfolding event.
At this moment, the final battle between humans and demons, deciding the future of this world, had begun in full swing.