After speaking with Tamayo, Yoriichi stood deep in thought in the courtyard for a long time. Only when the eastern sky began to glow with the first light of dawn did he return to the house, his clothes heavy with dew. He found Hiru sitting upright, engrossed in a medical text.
"Brother?"
"I spoke with Miss Tamayo about some matters."
Hiru set down his book, sat up straight, and waited for Yoriichi to speak.
"She said that to create a drug capable of killing you, she absolutely needs blood from your fully demon-transformed state." Yoriichi's expression remained calm. "But a fully demon-transformed you would likely assimilate her. So she asked me to help her obtain a sample of your blood."
"Ah... understood."
Hiru stood, shedding his outer garment as the marks of demon transformation gradually emerged upon him. Sharp claws, five centimeters long, sprouted from his slender fingers. Ferocious demon horns grew from his forehead, while eerie blue-gray patterns radiated outward from the horns, spreading across his entire body. His muscles became more defined, and his stature grew noticeably taller.
But the transformation stopped there. Compared to the demons he had hunted over the years, even in his fully transformed state, Hiru looked less intimidating than some ordinary minor demons.
His gray eyes met Yoriichi's as he raised a hand. "Did you bring containers, brother?"
Yoriichi nodded and produced two small porcelain bottles.
Hiru slit his wrist, letting blood drip into the porcelain bottles. Once both were filled, he ceased suppressing his healing ability. The demonic traits faded, and his body slowly returned to normal.
"Will two bottles be enough?"
"Yes. Too much would be difficult for Miss Tamayo to handle." Yoriichi sealed the bottles. "I need to go out for a while. Wait here for me. I'll return as soon as possible."
"Eh?" Hiru's voice carried obvious disappointment. "Aren't you taking me with you, big brother?"
"Sorry, I can't bring you this time." Yoriichi smiled and reached out to ruffle Hiru's hair. "Alright, I'm off."
Hiru watched Yoriichi's usual gentle smile, yet a sense of unease lingered in his heart. He instinctively extended his senses and discovered that after visiting Tamayo, Yoriichi had already left.
"Am I overthinking this..." Hiru furrowed his brow, eventually giving up on trying to decipher the deeper meaning behind Yoriichi's actions.
[Never mind. Big brother probably really has something to do.]
[Like going to inform the Demon Slayer Corps about the possible developments?]
[Or maybe read a book? Might discover new flavors before it vanishes?]
[Besides, big brother should be back soon, right?]
Hiru picked up his book and immersed himself in study once more.
...
Time passed imperceptibly for demons, so it wasn't until a month and a half later—when Tamayo arrived bearing newly developed medicine—that Hiru realized Yoriichi still hadn't returned.
Hiru merely instructed Tamayo to seal the medicine away for now, then began standing daily at the window, waiting for Yoriichi's return.
Observing from the shadows, Tamayo could clearly sense the demonic energy roiling beneath Hiru's calm surface, his emotions on the verge of eruption.
"Mr. Hiru..." Tamayo stood in the shadows, watching him remain motionless by the window for seven days straight. Concern filled her face. "Please rest for a while. Even as a demon, this will wear down your body. If you lose control waiting for Mr. Yoriichi before he returns, he'll be deeply hurt and blame himself."
The demonic aura surging around Hiru stilled for a moment. His gray, shuriken-like eyes turned toward Tamayo. For the first time in decades, she felt the overwhelming pressure of the Demon King and nearly collapsed to her knees. Still, she forced herself to remain standing.
"Please rest. I will notify you the moment Mr. Yoriichi returns."
Hiru's gaze soon shifted away. His voice was calm and distant. "Hmm, you're right. I'll rest for a while. I can't let my brother worry... Tamayo, if he returns during this time, come wake me immediately. Understood?"
"Y-yes."
Tamayo's voice trembled as she watched Hiru turn and walk back into the room. When he disappeared from sight, her legs gave out, and she sank to the floor. Once her body finally recovered from the sheer terror, Tamayo unconsciously pressed her palms together against her forehead, a faint sob escaping her throat.
[Please, Mr. Yoriichi, hurry back. I beg you. Without your restraint, that monster will truly destroy this world... Please, please hurry back. I truly beg you.]
...
Hiru lay beneath the warm futon in his undergarments, his hands folded neatly over his chest. Yet his pupils remained gray crosses.
He was utterly confused now, his inner turmoil threatening to spill over. He understood all too well that the greatest difference between demons and humans wasn't power—it was lifespan.
As a demon, his life could last hundreds, even thousands of times longer than a human's. But no matter how powerful Yoriichi was—strong enough to defy the curse of the Marked Swordsmen who perished at twenty-five—he could not escape the limits of human life.
[How old is Brother this year? Is he about to die?]
[But there was no shadow behind him... Why did he leave without a word? Wouldn't it be easier to let me handle things?]
[Ah, it's all my fault. Because I'm a demon, I've lost track of time... Now I can't even trace my brother's whereabouts.]
[But demons can turn humans into subordinates, can't they? Didn't Muzan also do this while searching for the Blue Spider Lily before my brother cut him down?]
[But if my brother knew I was harming humans, would he be disappointed in me?]
[Still... as fragile, helpless humans, isn't it their honor to burn their lives serving me?]
Hiru found himself drifting into these thoughts before frustration overtook him. He forcefully cleared the violent ideas from his mind and shut his eyes.
[Stop thinking. You've held on this long—don't let a short separation break your control.]
[Sleep now, sleep now. When you wake, Brother will be back.]
[This time, I must make Brother slay me, no matter what. If he shows mercy, I'll find humans to kill me instead. After all, Miss Tamayo's medicine can't truly end me. I can't let my longing for Brother's kindness blind me anymore.]
[Because my brother treats this world with love and compassion, while the existence of demons only brings ruin to its happiness. That's why I must die.]
[But I've overcome sunlight... and finally tasted real flavor for the first time. There are still so many things I want to do—to paint the morning light, to capture the evening glow, to...]
[So please come back, Brother.]
[If it weren't for you, I wouldn't know how to face death.]