Staring at the Black Coffin before him, Muzan Kibutsuji felt a deep, abyssal sense of dread welling up inside. Cautiously, he morphed his own blood into a sharp spear and thrust it toward the coffin—but there was no reaction at all.
Even when he unleashed a wide-range shockwave, the Black Coffin did not so much as tremble or shift an inch.
A cold sweat ran down Muzan's back. If that thing had been targeting him, the result would have been disastrous.
Yet, his fear could not conceal his exhilaration. A crazed, unrestrained laughter erupted from him, echoing across the ruins of the Ubuyashiki estate.
"Hahaha! The Priest Master! Ubuyashiki Yosuke! Now—finally—no one stands in my way anymore!"
Meanwhile, Inosuke had finally escaped back to the Butterfly Estate. The moment he stepped through the door, Hakuji and the others rushed up to him, surrounding him anxiously.
"Inosuke, where is Yōsuke-sama?"
The tear tracks on Inosuke's cheeks grew wet again. With a hoarse, trembling voice, he replied:
"Yōsuke-san stayed behind to face Muzan Kibutsuji and another guy called the Priest Master—all by himself. The battle didn't look good… It's my fault… I slowed him down."
The news sent chaos rippling through everyone in the Butterfly Estate.
Just then, a crow appeared—one of the Kasugai crows—and it transmitted to Hakuji and the others the memory of Muzan and the Priest Master's abilities.
The crow's message confirmed what Inosuke had said: Yosuke's situation was indeed dire.
Ume, her heart burning with anxiety, spoke up immediately:
"We have to go help Yosuke-sama—right now!"
Hakuji and the others prepared to depart at once.
But Gyomei Himejima's grave voice cut through the tension as he gazed toward the lightening sky.
"The sun will rise soon. The battle may already be over. None of you can withstand sunlight—going now would be meaningless."
"Get out of the way!"
Hakuji's voice burst with fury. Barely containing his rage, he shouted at Gyomei. The atmosphere instantly grew tense, blades of intent clashing between them.
The Butterfly Sisters, Gyutaro, Koyuki, and Ume all moved to Akaza's side—their intentions clear. Like him, they wanted to rush to the Ubuyashiki estate ruins and rescue Yosuke immediately.
"Everyone…" Tanjiro tried to ease the tension, but no words came to him.
Hakuji glared at Gyomei, his voice shaking with emotion.
"We're not like you! All of us were saved by Yosuke-sama—he's the reason we even have a life worth living! Now he's out there fighting for his life, and you expect us to just sit here and wait?!"
Gyutaro scratched at his face until it bled, his tone low and menacing.
"I don't care what anyone says. If someone tries to stop me—no matter who it is—I'll treat them as my enemy."
Gyomei's expression remained calm, his tone steady.
"I'm not trying to stop you. But if you go now, there's a high chance you'll fall straight into the enemy's trap."
As the standoff dragged on, a soft, almost ethereal voice drifted through the air.
"Everyone… I already know Yosuke-sama's situation."
They turned to see Kagaya Ubuyashiki and the Hashira arriving at the Butterfly Estate.
Kagaya explained calmly:
"After Tanjiro sent word through his crow that Yōsuke-sama had gone alone to rescue Inosuke, I immediately dispatched several scouting crows to the Ubuyashiki ruins. The battle there has ended. Muzan Kibutsuji remains unharmed."
The room fell silent—hearts sank.
Shinobu's voice trembled as she asked urgently:
"And what about Master Yosuke?"
Kagaya shook his head slowly.
"There was no trace of him at the site… only a pitch-black coffin. Muzan has summoned his Infinity Castle and stationed it above the ruins, guarding that coffin himself. Which means… Yōsuke-sama may be inside it."
At the mention of the coffin, everyone felt a chill in their chest.
The Butterfly Sisters, Hakuji, and the others immediately prepared to depart—to rescue Yosuke.
"Please wait, everyone," Kagaya called, stopping them. "I have a plan. Please, hear me out first."
Despite their impatience and dread, Hakuji and the others forced themselves to stand still and listen carefully.
Kagaya began to explain.
"Now, only three of the Twelve Kizuki remain. The time is ripe. It is time for our final battle against Muzan Kibutsuji.
If Yōsuke-sama truly is inside that coffin, Muzan will not leave his side. So my plan is this: once night falls, the Demon Slayer Corps will launch a full-scale assault to draw Muzan and his remaining Upper Moons into battle. During the chaos, Hakuji and the others will focus on rescuing Yosuke-sama."
Shinobu looked toward her sister uneasily.
"Sister… do we really have to wait until nightfall?"
Kanae couldn't decide. She turned to Akaza.
"Hakuji-san, should we wait for night and go with everyone, or act now?"
Hakuji forced himself to think clearly despite the boiling frustration inside him.
If he and the others—four demons plus the Butterfly Sisters—went now, facing Muzan and three Upper Moons alone, their chances of survival were slim to none.
But with the Demon Slayer Corps providing support, their odds would improve greatly.
Finally, he nodded heavily.
"Fine. Once the sun sets—we'll launch an all-out attack on Muzan Kibutsuji!"
Inside the Black Coffin, Yosuke opened his eyes to total darkness. There was no light—no sound. His body would not move.
He called out to the System, but there was no response. All he could do was slowly repair his damaged hearts.
As he focused on regeneration, a voice echoed in the void—it was the Priest Master.
"Between you and Muzan Kibutsuji, I find myself closer to you. In a sense… we are like brothers."
Yosuke frowned deeply.
"What are you talking about?"
They were both trapped in the same void, yet the Priest Master spoke with a calm, almost serene tone.
"Before demons ever appeared, the laws of this world were incomplete. Only when the first demon came into being—and when the destined child of the world finally slew that demon—would the world's missing laws be restored.
I was chosen by fate, bearing the power of the world's laws themselves, to guide the birth of the first demon. My Word Spirit and foresight are manifestations of that power.
But unexpectedly—you were chosen as well. The fragment of the world's law that was lost descended upon you, protecting you and granting you life when you should have died.
Even if the destined child were to slay Muzan Kibutsuji now, the world would still remain incomplete. Because the missing fragment of the world's rule—the part that would complete it—is within you, Ubuyashiki Yosuke."
"You and I are both chosen by fate—both bearers of the world's law. That bond surpasses even blood itself."
As the Priest Master spoke, realization dawned on Yosuke.
The System within his body—it must be that missing fragment of the world's law.
It also explained why the Priest Master had been able to predict precisely when his system-enhanced power would end.