Yosuke gently ruffled Nezuko's hair and spoke softly to her:
"Nezuko, I need you to use your Blood Demon Art on the person lying in that bed. Remember—summon that burning power from within."
Inside, Yosuke felt a twinge of unease. He worried that Nezuko might misunderstand his instructions and accidentally incinerate Kokushibō entirely.
Nezuko tilted her little head to the side, nodding as though she half-understood.
She walked up to Kokushibō's bedside and held her hand above his chest.
As droplets of her blood fell onto Kokushibō's body, scarlet flames immediately ignited.
Yet, despite their fierce heat, the fire did not burn through his clothes or the bandages wrapped around him. Still, the temperature soared, turning the entire room into a blazing furnace.
As time passed, Nezuko's forehead glistened with sweat—her Blood Demon Art: Exploding Blood consumed vast amounts of her own demonic energy and blood.
Zenitsu, whose hearing was sharpest, was the first to notice a change in Kokushibō.
"His heartbeat… it's getting stronger!"
When Nezuko's Blood Demon Art finally ceased, her body—drained from the heavy blood loss—regressed into her small, childlike form.
She toddled over to Yosuke and tugged at the hem of his pants.
Yosuke smiled fondly, scooping her up.
"Well done, Nezuko."
Nezuko rubbed her head against his arm affectionately, and Yosuke returned her to Tanjiro's care.
Shinobu Kocho examined Kokushibō's body. She noted that his breathing had stabilized, his vital signs were steady, and that the burning energy inside him had completely vanished.
After finishing her check, Shinobu said:
"All right. Let's give him some peace and let him rest."
Everyone quietly left the room.
Just as Yosuke was about to close the door, a weak voice called out:
"Yashiki… Yosuke."
Yosuke turned back and approached the bedside again.
"I'm here," he said softly.
"Do you… believe in the existence of souls?"
Yosuke nodded firmly.
"I do. I've seen people dear to me who have already passed away. In fact, it was Yoriichi who guided me to Swordsmith Village."
"I see…"
Kokushibō's gaze drifted as he recalled his encounters with his younger brother.
"I never truly believed that souls existed after death. I thought all of it—what I saw—was merely my own obsession.
"But when I stood before Yoriichi's grave, I saw him. That was the first time I faced my true heart.
"The second time was during my battle with Muzan Kibutsuji. When I was on the verge of death, I saw Yoriichi again. He lent me his strength—enough to perform the Sun Breathing I was never meant to wield, to fight against Muzan.
"And yet… I still failed."
A trace of bitterness crossed Kokushibō's expression.
"Even in death, Yoriichi still worried for me. I'm such a disgraceful elder brother."
Yosuke's eyes widened in surprise.
"So, the Sun Breathing—was it because of Yoriichi? Can a soul truly grant someone power?"
"As unbelievable as it sounds, I could feel it. The only reason I was able to use Sun Breathing was because of Yoriichi. As a demon, it should've been impossible. If I'd truly mastered it myself, I wouldn't have suffered such backlash."
Yosuke asked again, his tone grave:
"Why did you end up fighting Muzan on Swordsmith Village?"
Kokushibō's reply was calm but heavy.
"I once said that my status as Muzan's subordinate only lasted up until the point he found the Clan of the Divine Priest."
Yosuke's eyes went wide, his expression tense.
"You mean… Swordsmith Village was the home of the Divine Priest Clan—and Muzan has already found them?"
"Yes. Muzan must have known I betrayed him long ago. When I was about to slaughter the clan, he suddenly appeared and stopped me."
Yosuke's face darkened. He didn't know whether the Divine Priest Clan could help Muzan conquer sunlight, but he had to prepare for the worst.
After a long silence, Yosuke said quietly:
"For now, rest. You're safe here."
Then Kokushibō spoke again.
"May I… see that boy named Kamado Tanjiro?"
"Of course," Yosuke nodded. "He's just outside."
Yosuke stepped out and brought Tanjiro in.
Tanjiro was confused—he'd never met Kokushibō before. Why would he want to see him?
As Tanjiro stood beside the bed, Kokushibō gazed at him with tear-filled eyes.
"You really are like Yoriichi," he murmured. "I can feel it—your kindness, your gentleness… just like his."
Tanjiro didn't know how to respond. He simply stood quietly, listening.
"Tanjiro," Kokushibō said softly.
"Yes?"
"Could you… place your hand on my forehead?"
Tanjiro gently laid his hand on Kokushibō's brow.
Feeling the warmth of Tanjiro's palm, tears streamed down Kokushibō's cheeks as he whispered Yoriichi's name again and again.
From Kokushibō's scent, Tanjiro could sense boundless sorrow and regret. His tense shoulders relaxed, and he silently offered comfort.
A month passed.
Kokushibō's limbs had fully regenerated, though he could no longer perform Sun Breathing. He could still use Moon Breathing, but his power had diminished greatly.
The flames of Sun Breathing had burned away much of Muzan's blood within him, leaving him drastically weakened.
Originally, Yosuke had intended to inject him with his own blood to restore his strength—but Kokushibō refused.
"I'm tired," he said. "Like Yoriichi, I want to entrust my hopes to the future."
Yosuke respected his decision.
With that resolve, Kokushibō devoted himself entirely to teaching Tanjiro, Zenitsu, and Inosuke.
Though his power was only a fraction of what it once was, Kokushibō's centuries of experience as a warrior made his instruction incomparable.
Under the guidance of Yosuke, the Kocho sisters, Kyojuro Rengoku, Hakuji, Gyutaro, and Kokushibō himself, Tanjiro, Zenitsu, and Inosuke grew to the level of Hashira.
From Kokushibō, Tanjiro also learned that Sun Breathing contained a thirteenth form—an infinite sequence of all twelve forms used in seamless succession.
Although Tanjiro still couldn't yet perform the forms consecutively, his mastery of each individual form had reached perfection. He continued to train tirelessly toward that ultimate goal.