Although the medicine to turn demons back into humans had been successfully developed, it could not yet be mass-produced. This was because its key ingredient was the blood of either Nezuko or Michikatsu Tsugikuni.
Since Nezuko had already taken the medicine herself, that meant only Michikatsu could now provide the blood needed to create more doses.
Yōsuke summoned Hakuji, Gyutaro, Koyuki, and Ume to inform them of the successful development of the medicine and to ask if they wished to receive the injection.
All four refused without hesitation. Though unexpected, their decision was understandable. Their shared reason did not surprise Yōsuke—because they all had one common goal: Kibutsuji Muzan.
In the Infinity Castle.
After waiting impatiently for some time, Kibutsuji Muzan finally turned toward the Divine Master and snapped,
"Don't you claim to have the power to foresee the future? Tell me—has Ubuyashiki Yōsuke used the medicine to become human or not?!"
The Divine Master sensed that the time had come and activated his ability of foresight.
His brows furrowed tightly.
"I can confirm—it has failed. Ubuyashiki Yōsuke has not used the medicine."
Muzan slammed his fist down, shattering the table before him in fury.
"Damn it! I knew it! That man would never willingly abandon his power. What should we do next?"
The Divine Master remained calm and composed.
"In that case, we shall lure Ubuyashiki Yōsuke out—and when he appears, you and I will strike together and end him."
Muzan sneered disdainfully.
"Lure him? Hah. And who besides me could possibly have the right or the power to lure him out?"
The Divine Master replied abruptly,
"Don't you have a subordinate named Inadama Kaigaku? Send him to attack a village called Ōsumi."
Muzan's eyes narrowed.
"Why? Kaigaku's strength may be that of an Upper Rank, but he's nowhere near strong enough to draw out Ubuyashiki Yōsuke."
The Divine Master's tone was cryptic.
"Don't worry. Inadama Kaigaku is merely the bait—the wedge that will set things in motion."
Muzan frowned in irritation. He despised the Divine Master's riddling manner, yet as an ally of convenience, he restrained his temper and summoned Kaigaku nonetheless.
Kaigaku knelt before him, head bowed low. Muzan's cold, demonic eyes glinted as he issued the command:
"Kaigaku. Go and massacre the village of Ōsumi."
Kaigaku raised his head in surprise.
"You mean… simply slaughter the entire village?"
At present, only four members of the Twelve Kizuki remained. Common sense dictated that they should lie low and recover their strength. Attacking a village now was clearly a reckless move.
If luck turned against him, he might be surrounded by Hashira—or worse, encounter the demons serving under Ubuyashiki Yōsuke.
As for Yōsuke himself… Kaigaku didn't even dare to imagine facing him. Meeting that man would mean an immediate death sentence.
During his time as a demon, Kaigaku had come to understand Muzan's temperament—moody, calculating, and never one to put himself at risk.
So this sudden order to destroy Ōsumi Village didn't seem like something Muzan would normally command.
And since a mere village massacre hardly required the power of an Upper Rank demon, Kaigaku's eyes drifted toward the man seated calmly beside Muzan—the Divine Master.
Kaigaku suspected it was this mysterious individual's idea.
He couldn't help but wonder—this person, who was clearly not a demon—what kind of power or influence did he possess to sit as
an equal beside the ruthless and merciless Kibutsuji Muzan?
Seeing Inatama Kaigaku questioning him, Kibutsuji Muzan's fury surged up from deep within. However, given the current circumstances, it would not do to lose his temper—every Upper Moon was now an invaluable asset.
Suppressing his rage with effort, Muzan barked coldly,
"It's a simple order—wipe out the entire village of Ōsumi. Now go!"
Sensing the faint edge of anger in Muzan's tone, Inatama Kaigaku froze in terror. He immediately pressed his forehead to the floor.
"Y-Yes, Muzan-sama!"
Through Nakime's dimensional portal, Kaigaku was transported directly to the entrance of Ōsumi Village.
Even in the dead of night, the village was brightly lit. A bloodthirsty grin twisted Kaigaku's face. He relished the thrill of the hunt—and even more so, the exquisite taste of human flesh and blood.
As he stepped into Ōsumi Village, the slaughter began—a massacre without mercy or humanity.
Meanwhile, at the Butterfly Mansion, a messenger crow startled Tanjiro Kamado, Zenitsu Agatsuma, and Inosuke Hashibira awake from their slumber.
>"Tanjiro Kamado, Zenitsu Agatsuma, Inosuke Hashibira—listen carefully. Your next mission: head northwest to Ōsumi Village and slay the Upper Moon demon—Inatama Kaigaku!"
At the mention of that name, Zenitsu bolted upright, his face suddenly grave.
Tanjiro looked at him with concern.
"Zenitsu, are you okay?"
Zenitsu's eyes hardened.
"I'm fine… It's finally time to end this. I'll cut down Inatama Kaigaku—the one who became a demon."
His hand brushed gently over the haori that Sakonji Urokodaki had remade for him, his expression filled with quiet determination.
Without disturbing anyone else, the three left behind a letter and departed swiftly toward Ōsumi Village—to confront the demon and settle Zenitsu's past.
By the time they arrived, flames were already devouring the village. The air was thick with smoke, and desperate cries for help echoed endlessly through the night.
Kaigaku rampaged through Ōsumi Village, butchering its people without remorse. The louder their screams grew, the more his twisted, hollow heart brimmed with satisfaction.
He stepped on the head of a fallen woman. Not far away, her husband glared at him in hatred—but fear rooted him in place.
Kaigaku smirked, curling his finger in mock invitation.
"Come on then. I'll give you a chance—if you come here, I'll spare her."
The husband wanted desperately to rush forward and trade his life for his wife's. But his legs felt as if they had been encased in concrete—he couldn't move.
With a strangled cry of despair, the man turned and fled, abandoning his wife.
Kaigaku burst into laughter so intense that tears streamed down his face.
Watching the man's retreating back, he recalled the past—when Gyōmei Himejima had taken him in at the temple, raising him among the other orphaned children.
But after Kaigaku was caught stealing money, the other children betrayed him to Himejima, who expelled him from the temple. Misfortune followed swiftly—he encountered a demon soon after.
To save his own life—and to exact revenge—he crept back into the temple, extinguished the wisteria incense Himejima had lit to ward off demons, and lured a demon inside before fleeing into the night.
"That's right… This is how people truly are. To survive, anything is justified! I did nothing wrong—you were the ones at fault!"
He pressed down with his heel. The woman's skull burst like a watermelon beneath his foot.
"Thunder Breathing, Fifth Form: Heat Lightning!"
With a roar, Kaigaku unleashed scorching lightning, striking down the fleeing husband. A gaping, bowl-sized hole was blown through the man's chest; his lifeless eyes stared upward as his body collapsed to the ground.
Throughout Ōsumi Village, Inatama Kaigaku's deranged laughter echoed amidst the flames.