"Miss Tamayo, could you tell me more about Muzan Kibutsuji?"
"Yes, of course."
A flash of madness and hatred filled Tamayo's eyes as she recounted everything she knew about Muzan.
Yoriichi and Hiru listened patiently until she finished. Only then did Yoriichi speak again.
"May I ask you a few more questions, Miss Tamayo?"
"Please do." Tamayo straightened her posture, kneeling respectfully. "As long as it's something I know, I'll tell you everything without reservation."
"You said Muzan Kibutsuji is the progenitor of demons—that every demon was born from him?"
"Yes."
Yoriichi lifted Hiru down and set him on the ground. "But my younger brother became a demon through medicine."
Tamayo fell silent for a moment, as though deep in thought. "I remember Muzan once said that he was missing only one ingredient—the Blue Spider Lily—to become a perfect being, immune to sunlight.
He also mentioned that, when he was still human, his body was frail, and the doctor told him he wouldn't live long. Later, another physician spent years experimenting with medicine until he turned Muzan into a demon.
But Muzan was so enraged at being transformed that he killed the doctor on the spot. That's why he still fears sunlight to this day.
That's all I know—and I only know this much because I was a doctor. Muzan kept me alive so I could refine his medicine once he found the Blue Spider Lily, and he told me these things then."
"But I only took a powdered medicine I made myself," Hiru muttered, furrowing his brow. "If demonization through drugs is supposed to be a gradual process, then what happened to me? I transformed instantly."
"Could you tell me what ingredients you used?"
"Many—but all common herbs..."
Hiru listed the ingredients one by one, though he deliberately withheld the exact proportions.
"With just these herbs, long-term use might strengthen the body," Tamayo said thoughtfully. "Have you forgotten anything?"
Hiru paced a few steps, thinking carefully before replying. "There's also the powder I extracted from demons. You know how demons turn to ash under sunlight? I managed to collect that ash once.
It's hard to preserve and almost impossible to study, so I tried infusing it into my medicine, refining it into powder several times before mixing it together. Honestly, I've been doing that for a while, but I was my own first test subject. So I don't really know how much influence the ash had—or how it changed the formula."
"That must be the key." Tamayo's voice softened, calm yet reassuring. "Just as humans tainted by Muzan's blood instantly turn into demons, the same must have happened to you.
But because you ingested it differently, Muzan couldn't control you. You became an primordial demon—one independent of his will."
Hiru went silent, deep in thought.
So... he was actually a demon progenitor? But he felt so weak. Wasn't a Demon King supposed to be strong?
He thought of Muzan, who had been hacked apart by Yoriichi's blade.
Hmm. Pretty weak, actually.
Yoriichi spoke again. "You said those transformed by Muzan's blood are under his control—what do you mean by that?"
"Demons created by Muzan's blood cannot speak about him. If they try, he immediately senses it. Their bodies are destroyed from within, and they die in agony as the sun rises.
He holds absolute control over every demon born from his blood."
Tamayo's eyes dimmed with sorrow. "The severe wounds you inflicted on him must have temporarily broken his hold on me."
"If the Demon King dies, will all demons die with him?" Hiru asked. "Or at least, will new ones stop being born?"
"I'm sorry," Tamayo replied softly. "I only know that Muzan is the source of all evil. I don't know what will happen if he's slain."
"Brother," Hiru said, looking up. "Muzan was heavily wounded by you and fled in such humiliation. From what Miss Tamayo said, he probably won't appear again—not in your lifetime."
Yoriichi lowered his gaze. "It's still my responsibility..."
"Honestly, Brother, not again!" Hiru smacked Yoriichi's leg in frustration. "Stop blaming yourself for everything! With the power Muzan showed, if it weren't for you, those Demon Slayer Swordsmen wouldn't even have been able to scratch him."
"But the truth remains," Yoriichi said quietly. "Heaven gave me strength, yet I failed. And because of that failure, even if I enjoy a few peaceful years, countless more will die because of me."
He looked into Hiru's eyes, then raised his head. "The battle earlier must have reached far. The nearby swordsmen should be gathering soon."
Tamayo closed her eyes upon hearing that, ready to accept her death.
"Then you should become a demon too, Brother."
Tamayo's eyes snapped open. Yoriichi looked stunned, while Hiru's gaze was unwavering. Her heart pounded violently.
If someone as powerful as Yoriichi—stronger even than Muzan—were to become a demon, would humanity truly have any hope left?
"But Hiru," Yoriichi said softly, looking down at him, "when you became a demon, I was able to restrain you. But who would restrain me if I turned? If I became a demon, no one could stop me. What would happen to humanity then?"
"Then let's test it first."
Hiru lifted his head, smiling calmly. "I'll make another batch of demon-transforming medicine and give it to a notorious bandit. He'll take it and turn his fellow bandits into demons.
Then, we'll kill the first bandit—the one who took the medicine. If all the others he turned die with him, or lose the ability to create more demons, then when you're near death, I'll turn you into a demon. That way, we'll be bound to each other—restraining one another.
But if it doesn't work," he continued, his voice softening, "then you must make me a promise: before you die, you'll go with me to watch the sunrise one last time.
As for our dream... I'll entrust it to Miss Tamayo, who bears such deep hatred for Muzan."
Yoriichi's calm eyes turned to Tamayo. He was silent for a long while before finally looking back at Hiru.
"Alright," he said quietly. "I promise."