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A day later, the group arrived at a remote mountain village.
Two members of the Demon Slayer Corps stationed there rushed over the moment they saw the Hashira. They reported that while tracking a demon, they had suddenly watched it vanish—swallowed by what looked like a portal that opened into a dazzling, bustling city. The demon stepped inside… and the entire city disappeared with it.
Like it had never existed.
After hearing the report, everyone headed to the exact spot where the mysterious city had appeared.
There was nothing.
No trace. No distortion. No suspicious signs.
At last, all eyes turned to Alex.
He smiled casually. "Muzan has a subordinate named Nakime. Her Blood Demon Art lets her control the Infinity Castle. She can teleport anyone there, or open its entrance anywhere she pleases."
Shinobu frowned slightly. "A spatial ability like that is a nightmare. Can you track it?"
"Easy," Alex replied with a grin. "If a passage to the Infinity Castle opened here, space itself must've left a scar."
He drew out his weapon.
It was the first time the others had seen it up close—a magnificent greatsword, elegant and imposing.
Raising the blade, Alex spoke a fragment of a divine incantation:
"Here I swear: nothing shall exist that I cannot cut."
Though he possessed monster traits that allowed him to cast spells without chanting, this wasn't magic.
Authority was different. It was a rule of the universe itself—power belonging to gods.
He didn't need the full incantation. One line was enough.
In the next instant, his arm transformed into silver metal. Sakura-colored magic burst from his body and poured into the blade.
The Hashira stared, stunned.
This was their first time seeing Alex truly act—and he looked overwhelmingly powerful.
Cool, too.
He swung.
Space split apart with a thunderous tear, opening a massive rift.
On the other side—
The Infinity Castle.
The Hashira's eyes lit up. Their target was finally within reach.
No one burned brighter than Yoriichi Tsugikuni.
The last time, he had failed to kill Muzan and had been cast out by the Corps. This time, he would end it.
"Let's go," Alex said.
He stepped through first. The others followed immediately.
The spatial tear sealed behind them.
Alex didn't care. He casually unleashed a grand forbidden spell: Unlimited Blade Works.
The entire Infinity Castle was dragged into his domain.
He never liked fighting on someone else's turf. Much better to make it his own.
Now, no matter how Nakime manipulated the castle, there would be no escape.
—
The moment the castle was swallowed by the domain, Muzan sensed something was wrong.
And when he saw who had arrived—
His face drained of color.
"T-That's… Yoriichi Tsugikuni!" Muzan's voice trembled.
"Muzan," Yoriichi said calmly, his expression unchanged. "We meet again. This time, you won't escape."
His aura alone pressed down so heavily that Muzan struggled to breathe.
At that moment, Upper Rank One, Kokushibo, stepped out from a nearby chamber.
When his six grotesque eyes fell upon Yoriichi, they widened in disbelief.
"That's impossible! I killed you with my own hands. I cut your corpse in half! Why are you alive? And why do you look so young?!"
Yoriichi, brought from the past by Alex, stood at a time just after being expelled from the Corps. He knew nothing of what followed in that timeline.
But he could guess.
If history was fixed, then Alex's interference had split it. One timeline continued as it had. Another branched off.
Parallel worlds.
"If I had not killed you," Yoriichi replied evenly, "how could I possibly have died?"
"Then let's settle this once and for all!" Kokushibo roared, drawing his blade.
But before he could move, the seven male Hashira stepped forward as one.
"The Corps' traitor is ours to cut down!"
Elsewhere, Upper Rank Two, Doma, appeared beside Muzan, casually gnawing on a girl's severed leg. Blood smeared his lips. He looked utterly at ease.
"Well, well. Lord Kokushibo certainly has a lot of enemies."
Kanae Kochō stepped forward. "Doma. Do you remember me?"
He squinted. "You… I recall you died."
"Heaven must have taken pity on me," Kanae said, unsheathing her Nichirin blade. "It brought me back to kill you."
Shinobu, Mitsuri, Kanao, and Nezuko joined her side.
Muzan's eyes widened. "You've found a way to revive the dead, haven't you?"
They only smiled.
No one answered.
The battle erupted.
Yoriichi vs. Muzan.
The seven male Hashira vs. Kokushibo.
Kanae and the women vs. Doma.
Tanjiro and Genya vs. Nakime.
Inosuke and Zenitsu vs. Kaigaku.
And Alex?
He stood off to the side, watching.
This level of fight didn't require him. They all had their grudges to settle. If he stepped in, it would be over in seconds.
He even opened a livestream for his chat group to watch.
—
Unlike the brutal, desperate struggle of the original timeline, this battle was one-sided.
Yoriichi unleashed his self-created Breath of Combat and cut Muzan down in an instant, reducing him to fragments.
Kokushibo was powerful—but under Alex's training, every Hashira now stood on equal footing with him. The seven overwhelmed and executed him swiftly.
Doma, who delighted in devouring women, met his end at the hands of a united group of women. They cut him into nothing but scraps.
Nakime and Kaigaku soon followed.
Every demon was annihilated.
To ensure Muzan could never revive, Alex invoked the Authority Solar Sovereignty and summoned a blazing sun.
The Infinity Castle, along with the demons' remains, evaporated under its light.
When they exited, a notification from the chat group confirmed it.
Mission complete.
—
With the demons gone for good, the Demon Slayer Corps erupted into celebration.
They declared a three-day feast.
But Alex didn't have the luxury of time. After completing the mission, he only had twelve hours left in this world.
So after the first night's celebration, he gathered the Corps' leadership.
Kagaya Ubuyashiki and his wife Amane. All the Hashira. Tanjiro and his friends.
When everyone was present, Alex nodded to Shinobu.
She stepped forward and explained.
Alex was from another world. A favored of the gods.
He had come not just to help—but to recruit. He wished for the Demon Slayer Corps to follow him to Orario and become part of a divine familia.
The room fell into stunned silence.
They had known he was from another world—but this?
All eyes turned to Kagaya.
He smiled gently. "Muzan is dead. There are no demons left in this world. The Demon Slayer Corps has fulfilled its purpose. If you wish to venture into another world, I support you."
Excitement flickered across many faces.
Another world.
After witnessing Alex's power, who wouldn't want to grow stronger?
Tengen Uzui suddenly raised a hand. "If we go… can we bring our families?"
He had three wives. There was no way he'd abandon them.
"Of course," Alex replied.
Uzui's wives were skilled kunoichi. With a blessing, they could easily grow into high-level adventurers.
Smiles spread through the room.
—
Before departing, Alex accompanied Tanjiro and Nezuko back to their old home.
They dug up the graves of Tanjiro's parents and siblings.
And revived them.
After enduring death and separation, the Kamado family reunited in tears and laughter.
Tanjiro had planned to bring them to Orario as well.
But his parents shook their heads.
They would remain in this world.
The demons were gone. There was no more danger.
And for the first time in a long, long while—
Peace truly belonged to them.
"..."
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