Yōsuke was racing toward Narrow Isle at full speed.
When the figure of Tsugikuni Yoriichi had suddenly appeared before him, he had hesitated for a moment—wondering if it might be one of Kibutsuji Muzan's tricks meant to deceive him, to lure him into a trap on Narrow Isle.
But that brief doubt soon vanished. Muzan, who had never conquered the sun, would never risk attacking Yōsuke directly. Both of them knew very well: neither could kill the other—unless one of them dragged the other into sunlight to die together.
What truly dispelled Yōsuke's suspicion was the aura of the man who appeared before him. No illusion could possibly reproduce it.
Pure, calm, gentle, and steadfast—that was how Yōsuke had always imagined Tsugikuni Yoriichi's soul.
Yōsuke had long suspected that in this world, human souls did not simply disappear after death. He had seen visions before—of those who were once dearest to him: his parents, Kaori…
If what Yoriichi said was true, then Yōsuke could be sure—souls bound by powerful emotions did not reincarnate, but instead lingered in the world of the living, staying beside those most precious to them.
When Yōsuke arrived on Narrow Isle, the first thing he saw was fire—raging flames consuming the island's center, black smoke and the acrid stench of burning filling the air.
He entered a building that had been reduced to scorched ruins—and found a charred body lying motionless on the ground.
Up close, he could barely recognize it. If not for the six eyes on the man's face, Yōsuke would never have known—it was Tsugikuni Michikatsu.
At that moment, Michikatsu still clung to a single, flickering breath of life. His limbs had been completely carbonized into ash; his body blackened beyond recognition. Had Yōsuke arrived even a little later, there would have been nothing left to save.
To stop the carbonization from spreading, Yōsuke began injecting his own blood into Michikatsu's body again and again.
Under the protection of Yōsuke's blood, the carbonization temporarily halted—but his condition remained dire.
Without a moment's delay, Yōsuke lifted Michikatsu into his arms, unfurled the blood-red wings on his back, and soared toward the Butterfly Estate.
When the Kocho sisters and Tamayo saw the burnt, barely human figure he carried in, all three were stunned.
Shinobu asked in disbelief,
"Master, who is this person? How could someone be so terribly injured?"
Yōsuke replied gravely,
"Tsugikuni Michikatsu… also known as Kokushibō."
"Kokushibō—the Upper Rank One of the Twelve Kizuki?!" Shinobu exclaimed. "Master, why did you bring him here? Is he… for research?"
Yōsuke shook his head.
"No. Michikatsu betrayed Kibutsuji Muzan. I brought him back to save him."
Kanae blinked in surprise.
"Betrayed him? But shouldn't the curse inside him have destroyed his body on the spot? Why does he look like he was… burned?"
Yōsuke speculated,
"Most likely, Michikatsu managed to break Muzan's curse on his own—just like Nezuko did."
Tamayo examined the wounds carefully, her expression darkening.
"These burns… they look like the result of Sun Breathing."
Shinobu's eyes widened.
"What? That's impossible! Other than the late Yoriichi and Tanjiro now, who else could use the Breath of the Sun? Don't tell me… Tanjiro did this?"
Yōsuke shook his head again.
"No. These aren't external wounds. They look more like backlash—burns from within."
Tamayo's pupils dilated, her face filled with disbelief.
"Backlash? You mean… Michikatsu used the Breath of the Sun himself? That's impossible! He's a demon—he shouldn't even be capable of using it!"
Yōsuke sighed, spreading his hands.
"I don't know the details either. That's why I need you all to do everything you can to save him. We'll find out the truth after."
And so, the treatment for Tsugikuni Michikatsu began.
Yōsuke could not leave even for a moment—his blood was the only thing keeping Michikatsu's body from crumbling into ash.
Once again, it was time for Yōsuke to suffer through his least favorite role.
As the Kocho sisters and Tamayo began discussing complex medical procedures, Yōsuke stood silently aside—completely lost. All he could do was serve as a living blood transfusion source whenever they called out for him.
"We need to remove all the carbonized tissue first," Shinobu said, "and make sure the wounds don't become infected."
In this modernized era, medicine had advanced greatly—surgical instruments and treatments were readily available.
With delicate precision, Shinobu used fine tweezers to pick away the layers of burnt flesh bit by bit.
Kanae rinsed each area with disinfectant, cleansing the wounds to prevent secondary infection.
Meanwhile, Tamayo mixed restorative medicines for the next stage of treatment.
Yōsuke stood there blankly, watching the three women work tirelessly, only stepping forward when told to infuse more of his blood into Michikatsu's veins.
The treatment lasted for eight long hours. Finally, they were done.
Michikatsu now lay on the bed, swathed in bandages from head to toe like a mummy—but even so, his condition remained precarious.
Tamayo's expression was grim.
"We've cleaned all the wounds, but the internal burning hasn't stopped."
The Kocho sisters fell silent, deep in thought, trying to devise a way to counteract the continued burning within his body.
For now, they were at a loss.
But then Yōsuke remembered someone—someone who might be able to help.
He turned to Shinobu.
"Where are Tanjiro and the others right now?"
"Tanjiro and his group are currently on a mission with Kyōjurō Rengoku. Hakuji went along too—he said he was bored and wanted to join them."
"Hakuji's with them too? That's perfect!" Yōsuke said, visibly relieved.
Kanae looked puzzled.
"Master, what do you mean? Are you saying Tanjiro and the others can treat Michikatsu?"
Yōsuke nodded slightly.
"Do you remember Nezuko's Blood Demon Art?"
The three women froze. Realization dawned simultaneously on their faces.
"You mean…"
"Exactly. Nezuko's Blood Demon Art: Exploding Blood—its flames burn only what she chooses to burn. If the thing causing Michikatsu's body to carbonize is some kind of lingering energy or curse, then maybe Nezuko's flames can counteract it."
The idea made sense, and all three nodded in agreement.
Yōsuke immediately sent word through a Kasugai crow to Hakuji.
Upon receiving the message, Hakuji relayed it to Tanjiro, Nezuko, Zenitsu, Inosuke, and Rengoku. Without hesitation, the five abandoned their mission and hurried back to the Butterfly Estate.
When they arrived, they went straight to Michikatsu's room.
"Yosuke-sama! We've returned!" Hakuji called out as he entered.
Rengoku looked at the mummified figure on the bed, curiosity in his fiery eyes.
"So this is the former Upper Rank One, Kokushibō?"
Inosuke shuddered involuntarily.
"That guy… even half-dead like this, his presence still makes my skin crawl."
"He's done for, isn't he?" Zenitsu said, his keen hearing picking up only the faintest heartbeat.
Yōsuke raised a hand to quiet them.
"Enough talk. You're right—the situation is dire. Tanjiro, let Nezuko out. She's our only hope now."
Tanjiro nodded firmly, setting down the wooden box on his back.
Nezuko climbed out, her body returning from its small form to her normal size.