"Fine. I've been wanting to test my own strength anyway."
Hiru glanced up at the darkening sky before turning his gaze back.
"Let's finish this before the rain starts, then?"
Sakura Yakushi held her sword in one hand and took out two small vials with the other. Tossing one to Yato, she opened the other and drank it down.
"Alright then. If you can resist the urge to devour humans before the rain hits, I'll at least acknowledge you for now."
"Pah! That's bitter! What did you give me?"
Yato stuck out his tongue and tossed the empty vial aside in disgust.
"It's a potion that temporarily boosts rare blood concentration—enough to make an ordinary person smell like they have rare blood. You know how frustrating it is when demons suddenly want to run away mid-battle? So I developed this medicine specifically for that~"
Sakura Yakushi smiled brightly.
"But since it sometimes attracts more demons, I've never made it public."
"...Women really are terrifying."
"Mr. Yato, I heard that clearly this time. While I may learn from you about Breathing Styles, words like that make me angry, you know?"
As the two bickered, Hiru twitched his nose in slight confusion. The scent hadn't actually intensified at all.
"Ready—here I come!"
Sakura Yakushi had still been five meters away when she spoke, but before her words fully left her mouth, the flash of her blade was already before Hiru's eyes.
[So fast.]
Hiru's pupils contracted sharply. He transformed in an instant and barely dodged the blow, though a strand of his hair was still sliced away.
"And me too."
A sharp tingle of warning flashed across the back of Hiru's neck. He ducked low just as a blade swept through the air above him.
[They're serious.]
He quickly retreated, but the two didn't give him a moment's respite. Their coordinated strikes came crashing down again.
"Breath of Wind, First Form—"
"Breath of Mist, First Form—"
One fierce, one elusive—both forms melted seamlessly into the air around them. Their blades shimmered as they stepped forward in unison, attacking from both sides.
"Dust Whirlwind, Cutting Slash!"
"Distant Mist Falling from the Sky!"
Hiru instinctively prepared to use a Blood Demon Art, but stopped himself, choosing instead to keep retreating, dodging each slash by a hair's breadth.
Watching from the sidelines, Iwayuki sighed softly.
"Mr. Hiru truly is admirable in certain ways."
"What are Yakushi and Yato doing? Why haven't they finished off that demon yet?"
Hanyu Ichiyo said impatiently.
"If it were me—"
"Mr. Hanyu, this match is a test, not an execution," Oborozuki said calmly, her eternally gentle eyes fixed on the fight.
"And Mr. Hiru hasn't used his Blood Demon Art once. Do you know what that means?"
Hanyu Ichiyo snorted.
"It means the demon at least keeps his word?"
"No, I think what Mr. Oborozuki meant is that it proves what Mr. Hiru said about Muzan Kibutsuji's strength!"
Oborozuki tilted his head awkwardly.
"Mr. Rengoku, please don't speak so loudly."
"Ahem, my apologies!"
Rengoku Tetsushiro laughed awkwardly, lowering his voice.
"Mr. Hiru once said something like this—'Ordinary swordsmen can't even react to his attacks. Such strength still isn't enough to harm Muzan.'
I've never seen Muzan myself, but judging by Mr. Hiru's own power, I doubt even if Mr. Yato and Miss Yakushi activated their Slayer Marks and fought to the death, they could truly injure him."
"That sounds like an exaggeration, doesn't it?"
Keijin said, plucking a blade of grass and holding it between his teeth.
"That demon named Hiru hasn't used a single Blood Demon Art, and Yato and Yakushi haven't used any sword forms beyond the First. Don't you think you're overpraising him, Mr. Rengoku?"
"Not at all! After witnessing Mr. Yoriichi's swordsmanship firsthand, I have no doubts about his description of Muzan Kibutsuji!" Rengoku's voice rose in excitement again, his face glowing with admiration.
"It was truly magnificent!"
While Rengoku eagerly recounted the brilliance of Yoriichi's sword techniques, Yoriichi himself remained silent, his gaze fixed on the battle.
He noticed Hiru's eyes repeatedly flick toward the self-inflicted wounds on his opponents. His breathing had grown ragged, his demonic energy flaring and suppressing again and again, and faint growls began rumbling deep in his throat.
"Well, well... looks like the medicine is kicking in," Sakura Yakushi said with another bright smile as she swung her sword.
"It must be tough holding back, right? Mr. Hiru, how about you stop pretending and attack seriously? After all, we're both incredibly nutritious meals. Isn't that right, Mr. Yato?"
Yato: ...
Yato found her utterly insane. He didn't respond—just cooperated silently, attacking in sync to further limit Hiru's movement.
"I'm not drinking your blood, woman."
Though his body bore no visible wounds, Hiru's forehead was slick with sweat, and his haori hung in tatters.
"Ha! Drinking your blood would corrupt my soul."
"Oh? I didn't quite catch that, Mr. Hiru?"
"I said drinking your blood would absolutely corrupt my soul," Hiru panted, dodging another thrust.
"What's wrong? Angry now?"
"Not at all! I just want Mr. Hiru to earn recognition—so I can study you~"
"Then forget it. I like research, but I hate being the subject."
Hiru ducked under Yato's blade and charged straight toward Sakura Yakushi.
"I think it's about time I fought back."
"Then come and try~"
For the first time, Hiru met a blade head-on. His sharp nails scraped against the edge, producing an ear-piercing screech. Sakura's expression hardened as she spun her sword horizontally.
"Breath of Mist, Third Form: Scattering Mist Splash!"
A milky haze spiraled around her sword—but the motion froze mid-turn as Hiru's hand pierced through the mist and seized her wrist.
"Got you."
He tightened his grip, trying to wrench the sword from her hand.
But Sakura didn't panic. Instead, she shifted with the force of his pull, slamming into Hiru's chest as she unleashed her next attack.
"Mist Breathing: Fourth Form – Advection Slash"
Thick fog billowed across the field, instantly obscuring everyone's sight.
Yato dove into the haze, twisting his sword hilt as white mist burst from his lips.
"Wind Breathing: Second Form – Claw, Kado's Wind!"
Clang! Clang!
Two sharp impacts rang out beside Hiru's ears. When the fog dispersed, Yoriichi was standing behind him—while both Yato and Sakura's blades lay snapped clean in two.
"That's enough."
Yoriichi sheathed his sword, frowning slightly.
"As a test, it's sufficient. Hiru, let go."
Sakura clutched her swollen wrist, her face full of disbelief as she looked at Yoriichi.
"That speed was... unreal."
Yato, unsurprised by Yoriichi's strength, glanced down at his broken sword, looking awkward.
"Ahem, when I saw Sakura get grabbed, I kinda forgot this was a test. Sorry about that."
"It's fine." Hiru rubbed his temple, still suppressing his hunger.
"Honestly, I wanted to bite you during the first test anyway. So we're even."
"Wait—so Mr. Hiru wasn't affected at all?" Sakura smiled sweetly again.
"For a demon, rare blood should smell absolutely irresistible, right?"
"Yeah... I was practically drooling."
Hiru exhaled, his demonic traits fading except for his gray eyes. Sweat still beaded across his forehead.
"But I ate plenty of wild animals before coming here, and I sealed my hunger in advance, so I managed. Still, what was that medicine?
At first it smelled like thirty people, but as we fought, it got stronger—by the end, it was like a hundred."
"Just a slightly improved stimulant," Sakura said, sighing as she stared at her broken sword. "Ah, Mr. Tomohisa is going to scold me again..."
"I didn't even say anything, so what are you complaining about?"
Yato sighed, picking up his own broken blade.
"Mr. Yoriichi was using a standard Nichirin blade, wasn't he? That's... impressive."
"I told you, my brother is the strongest! Even if all of you teamed up, you couldn't beat him!" Hiru lifted his chin proudly behind Yoriichi.
"And yet you dare criticize him? How ridiculous."
Yoriichi sighed softly.
"Hiru."
"I'm not wrong!"
Hiru huffed.
"Even though I was only clan head for two years, I've always been fair and objective when judging people. Even if someone wrote a story about my brother and the Demon Slayer Corps, no one would say he was at fault! Though... they probably wouldn't blame the Corps much either."
"You..."
Yoriichi shook his head and turned to Yato and Sakura.
"Apologies. I may have used a bit too much strength."
"It's understandable."
Yato waved it off.
"But Yoriichi-san, shouldn't you replace your Nichirin Blade? You could have the smiths forge you a new one."
Sakura nodded.
"Indeed. A swordsman like you deserves a proper weapon. It would make your path to slaying demons much smoother."
Though most of the Hashira—aside from Rengoku and Oborozuki—still regarded Hiru with suspicion, they couldn't deny what they'd witnessed. Yoriichi's strength had earned their respect.
They knew they couldn't kill Hiru under Yoriichi's protection. The best they could do was arm Yoriichi with a stronger blade to ensure he could continue keeping Hiru in check.
"My fighting spirit's rising too!" Keijin spat out the grass from his mouth.
"After the Hashira Meeting, spar with me, Yoriichi-san!"
Hanyu Ichiyo turned away with a scowl.
"So you really are that strong, huh... Hmph. I suppose we'll have to share responsibility for Muzan Kibutsuji, then. As for this demon... tch. I'll let him live for now."
"Well, aren't you generous, you yaksha-faced swordsman."
"Hah? You trying to lose your head today?"
Hiru raised his chin behind Yoriichi.
"Heh, I've got my brother!"
"Even if it's a bit out of place to say it now, Mr. Hiru's technically a demon—so you should say you're a demon with a brother!"
"Shut up, you tone-deaf owl!" Hiru huffed, glancing down at his torn clothes.
"Ugh, my haori's in shreds... though it wasn't really mine to begin with."
Yoriichi reached out and gently ruffled his brother's hair, saying nothing.
"Um," Ubuyashiki Asahi spoke up hesitantly, "Why did Mr. Hiru say that to me earlier?"
Hiru blinked, tilting his head.
"Hmm... I guess because I saw my own shadow."
Ubuyashiki Asahi tilted his head in confusion. What did he mean by that?
"Anyway, enough about me. Weren't you all discussing Muzan Kibutsuji?"
Hiru crossed his arms.
"That's what really matters—and Mr. Yato, Miss Yakushi, please step back a bit. I'm starving, and I'd rather not drool in public."
Everyone: ...
...
Afterward, Yoriichi described his battle with Muzan in detail, handing over his written report and all known information to the Demon Slayer Corps.
"You let a demon that's eaten people escape?! Are you insane?!"
Facing Hanyu Ichiyo's accusation, Yoriichi quietly clenched his hand.
"Miss Tamayo harbors deep hatred toward Muzan Kibutsuji. I believe she will make great contributions in the hunt against him.
I promised Hiru that if our experiment fails, his life will end alongside mine. But Muzan, at his full power, is beyond what even trained swordsmen can handle.
Only demons truly understand demons. Doesn't the incense Hiru created already prove that?"
"Ah—" Sakura raised her hand.
"Mr. Yoriichi, what experiment are you talking about?"
"It's..." Yoriichi lowered his gaze, sorrow flickering in his eyes.
"An experiment concerning a hypothesis about the Demon King—and the fate that awaits Hiru and me."
"If my brother doesn't want to say it, I'll explain," Hiru sighed.
"In short, there are two possible outcomes. First, if I can create a medicine to turn demons back into humans, I'll hand over all my formulas—including the one for creating demons—to the Demon Slayer Corps. Then I'll live out my life as a normal human. Second, we'll test whether, after a human becomes a Primordial Demon, slaying that Primordial Demon will also kill its descendants. If not, we'll see whether it still has the power to infect humans."
"Primordial Demon? What does that mean?"
Keijin frowned.
"Aren't demons just divided by whether they can use Blood Demon Arts or are Demon Kings? And didn't you become a demon because of Muzan?"
Hiru shook his head.
"Half right. But in my brother's sight, my body structure is the same as Muzan Kibutsuji's. No other demon, no matter how powerful, shares this.
Simply put, even if my head is severed, I won't die—unless it's by my brother's blade.
So theoretically, I also possess the ability to create demons. Those I turn would be my descendants—completely unrelated to Muzan."
"If you're the same as Muzan, shouldn't you be dead already?"
"Shut it, you shorty! Interrupt me again, and I'll slap you so hard not even my brother can stop me!"
"You—!"
"Hiru, please continue."
Iwayuki calmly restrained the fuming Ibuki with one arm, his face expressionless. "Tell us more—about the experiment."