Byōga was miserable.
Was the woman chasing relentlessly behind him really from the Demon Slayer Corps?
None of the swordsmen he had fought before had been this ridiculous! She carried a weapon taller than herself and could still sprint at full speed.
Where were the laws of physics? Even a demon might not be able to lift that enormous sword!
And that armor still smelled of an apex predator. His attacks barely tickled it.
Cheats! She must be cheating! Tanky as hell, insane damage, and maxed-out movement speed. How was anyone supposed to play against that?!
Miserable. Utterly miserable.
After Koyuki died, Byōga had understood one thing: he had to get stronger!
Eat more people, or sooner or later I'll end up like that coward. No wonder that useless bitch was Four and I'm Three.
I've got more ambition than those bottom-feeding Lower Ranks!
So he had carefully laid traps in Tsutaya Village and cautiously devoured flesh and blood.
As long as he ate enough people, he would eventually gain complete control over this body. Then he might even leap straight into the Upper Ranks.
Sharing a body with two other morons was infuriating, but the power it offered made up for everything-as long as he could fully control it!
To that end, he had even driven a Nichirin Blade into his own body to suppress Rokuro's will.
The thought of becoming an Upper Rank and grinding that bootlicking Lower Rank One into the dirt filled Byōga with delight.
Then someone like this had shown up and effortlessly destroyed the miraculous body formed from three Lower Ranks.
Was this a fucking joke?!
"Shut the fuck up, all of you! Lose that walking disaster of a woman first!" Byōga roared inside the mind controlling the Deer-Body Stitching Abomination, forcibly suppressing Rokuro's spite and Kamanué's wailing.
Heaven always leaves a demon a way out!
He had climbed all the way to Lower Rank Three. Surely heaven favored him, too.
Just a little faster! Once my regeneration fully recovers, or I find more flesh... somehow...
The thought had barely entered his mind-
Whoosh! Whiz-!
An inconspicuous black speck flew in front of him with a faint whistle through the air.
What the hell was that?! Had that woman gotten so pissed off she missed?
All four eyes fixed on the strange little object, wondering what trick the woman was pulling now.
Boom-!!!!!
A violent burst of searing white light erupted in the darkness, bleaching everything within dozens of meters a blinding, ghastly white.
"Aaaaaagh-who the FUCK threw that flash?!!!"
"Help! My eyes!!!"
"There's a Tiga at A long! Tiga, aaaaaah!" (Crossed out.)
"I can't see anything! Keep those legs moving, you two morons!"
Three voices simultaneously erupted inside the head in screams so shrill they warped. Even demons temporarily lost their sight before that sudden, intense light.
The dizziness from losing its vision sent the fleeing abomination staggering violently.
With a thud, its already top-heavy body lost its balance entirely and crashed into a patch of withered bushes, snapping several branches.
Byōga knew.
That was it. Time to say goodbye to this beautiful world.
It's all those useless bastards, Lower Rank Two and Lower Rank Six's fault. If I'd stabbed their wills to death with the Nichirin Blade sooner, I'd be far stronger now.
Ah, I'm just too good a demon. Too softhearted.
No! It's that cheating woman's fault! If any other Hashira had come, I could've devoured them!
The crude junction between the deer's neck and the demon head groaned under the strain. Thin tears split the deer hide and stitched flesh.
"Run! Go on, keep running!"
The Sapphire Star slowly emerged from the shadows of the trees, glaring furiously at the deer-bodied, demon-headed abomination as it screamed in chaotic agony.
"Look at this mess you've made! After tonight's fight, the mountain god's fines will probably pile up into next year. I can't afford that. I really can't." She shook her head.
"So-I've decided to waive my overtime pay and send you straight on your way! Remember to reincarnate as environmentalists next time!"
"Urgh... aaaaah... you... fucking moron..." Byōga struggled to form words through the agony and rage. "Where... where'd that... flash come from?!"
He genuinely couldn't understand where this woman kept pulling all those bizarre things from. He hadn't even seen a backpack!
"Well, well, what a filthy little mouth! It was just a flash bomb. Don't sweat the details." The Sapphire Star shrugged, her hand rummaging for something else.
"Be good and relax-dizziness is normal."
Riiip.
"Aaaaaagh-what is that?!" The overlapping screams of Byōga, Rokuro, and Kamanué instantly changed pitch.
Byōga had imagined many possibilities for what the woman would do to him.
Would she curse him? Say he had eaten so many of her friends and family... yes, many of the swordsmen he had eaten before had been like that.
Or would she simply cut off his head? That wasn't entirely unacceptable. He had been driven into a corner, after all, though he bitterly resented it...
Or would she wait until sunrise and let the sun burn him alive? Given that woman's bizarre tendencies, that wouldn't be surprising either...
But...
Shhk-!
Something plunged directly into his brain.
Elderseal exploded from the puncture point, violently invading the demon's entire body.
They could clearly "hear" the inexhaustible, accelerated regeneration born of Muzan's original blood snapping apart inside them.
Every movement of the enormous Deer-Body Stitching Abomination, which had still been struggling and writhing, instantly froze.
The wildly squirming buds of flesh and the tissue fluid trying to seal its wounds solidified completely, losing all vitality.
In the study of a lavish villa elsewhere.
"Aaaaaagh-!!! Holy shit, is Yoriichi attacking me???"
Muzan Kibutsuji, who had been sitting upright, abruptly clutched his temples, flopped onto the floor, and writhed.
His extraordinarily handsome face twisted with agony and fury. His crimson slit pupils contracted sharply, as though invisible giant claws were viciously tearing at his nerves.
The blood connection that allowed him to sense every lesser demon had, in that instant, been invaded by a strange force crashing in from the primal wilderness. The three threads of life connecting him to Lower Rank Two, Lower Rank Three, and Lower Rank Six were severed at their roots!
Losing the connection was one thing. Muzan didn't care about those three useless fools.
Far worse was the pain and weakness flooding his mind, as though some terrifying, ravenous, ancient being that craved the destruction of all life were gnawing at him.
It hurt just like when Yoriichi had finely diced him into mincemeat all those years ago.
"Those three useless bastards! What trouble have they gotten me into now?!" Rage instantly swallowed Muzan's reason.
He went berserk. The exquisite screens surrounding his elegant cushion, the mountains of thread-bound ancient books, the precious porcelain vases... everything within reach of his power instantly turned to dust!
"My child?! What's wrong, my child?!" An elderly woman's panicked voice came from the doorway. Alarmed by the tremendous commotion, his adoptive parents pushed the door open in concern.
Muzan's crimson slit pupils, stripped of every human quality by his rage, glanced toward the two terrified mortals in the doorway as though they were insects.
Pop! Pop!
Two muffled bursts rang out, and a thick mist of blood spread through the room.
"Damned humans! Don't interrupt me now!" Muzan painfully rubbed his temples, his nails slicing straight through his own skin.
What had happened? Muzan couldn't understand.
The Lower Ranks were all useless, so he had fused three useless fools into a single mass. Granted, three useless fools together could at best become one big useless fool.
But that body should still have been able to handle a lone Hashira with relative ease.
Honestly, Muzan had been rather pleased with his masterpiece. Having "perfectly" stitched three Lower Ranks together, he had even admired himself for being so well-read.
So what exactly had they encountered?
He had spent the entire day searching books for legends of the Blue Spider Lily and hadn't had time to look through those three fools' eyes.
He had been reading quite happily, and had just spotted the words "blue spider lily..." in a book.
I was getting excited! A clue about the blue spider lily! The Blue Spider Lily, holy shit! I'm saved, hahahaha!
Then searing pain had flooded his mind, as though Yoriichi were crawling around inside it, trying to pull every fold of his brain flat.
Worse still, his outburst just now had reduced the book in his hands to scraps.
It's over... can I piece it back together...? Didn't I just see the Blue Spider Lily in that book...?
Back in the mountain clearing.
"Whew... finally settled down... Nergigante really is in a class of their own." The Sapphire Star dusted off her hands and drew her Hunter's Knife.
A spike protruded from the demon's forehead.
It was a regenerative spike from Ruiner Nergigante, brimming with savage Elderseal and regenerative power that perfectly counteracted the demon's own regeneration.
In other words, the head was currently in a state where it could neither die nor truly be considered alive.
"It's ugly, sticky, and disgusting... but it's still a rare specimen. It'll definitely be useful experimental material for the Demon Slayer Corps..." She muttered in disgust as she swiftly brought her knife down.
Slice! Slice! Slice!
After several clean cuts, the head containing the twisted trinity of Lower Rank Two, Three, and Six was completely severed.
Black-red blood dripped from it, giving off an even stronger stench and a faint, strange burnt odor forcibly suppressed by Elderseal.
Wrinkling her nose, the Sapphire Star pulled out a thick, tough piece of tanned Brute Wyvern hide.
She deftly wrapped the head, still dripping strange slime, tightly in it and tied it shut.
To be safe, the Sapphire Star scattered another large handful of Herbal Lifepowder into the air, neutralizing the last traces of poisonous mist.
"And that pile of rotten meat-if it sets the mountain on fire, I'll be in prison for life!" Once she had finished packing up, the Sapphire Star returned to the Burn Site.
Only two thick heaps of black ash remained. The wind stirred up the final scraps. The ground was charred and cracked, all vegetation within a dozen meters had withered, and farther out stood severed stumps and pits corroded by poisonous blood.
After confirming that no demonic aura remained, she breathed a sigh of relief. But her face fell as she surveyed the devastated forest.
"I reflect on myself three times a day... today's fight was far too sloppy. I caused so much environmental damage..." The Sapphire Star irritably kicked the scorched earth.
"That's why I hate the kind who resort to ambushes and changing zones whenever they're stumped! Can't they just fight me head-on?!"
Not long afterward, as dawn broke, a heavy atmosphere hung over the Council Chamber at Demon Slayer Corps Headquarters. Several Hashira stood or sat, reporting on recent demon activity. The demons had grown more active lately, and injuries had increased. Fortunately, thanks to the medicine provided by the Sapphire Star, no Corps members had died...
"Flap! Caw-!!!"
A Kasugai Crow with disheveled feathers, looking as though it had flown a great distance at full speed, hurtled through the window. It stumbled and nearly skidded several meters across the smooth floor before flapping its wings to steady itself.
Without stopping to straighten its feathers, it opened its beak wide.
"Report-caw-! Behind Tsutaya Village! The Jungle! Caw-!!"
The Hashira giving their reports immediately turned their attention to the seemingly frantic crow.
The Wind Hashira's hand was already on his Nichirin Blade. For a Kasugai Crow to lose its composure like this, something serious must have happened!
Even the ever-gentle and composed Oyakata-sama, Kagaya Ubuyashiki, leaned forward slightly, his pale face growing grave.
The Kasugai Crow's tiny, beanlike eyes widened until they seemed about to pop out.
"Lady Sapphire Star! Encountered an unprecedentedly powerful enemy! Confirmed!"
That powerful woman had encountered a formidable enemy? No, as Hashira, they had to go help her immediately!
It was as though all the air had been sucked out of the Council Chamber. Everyone held their breath.
Every feather on the crow's neck stood upright like an explosion of thorns as it screamed with almost all its strength.
"Enemy leaders!! Confirmed-Lower Rank Two, Rokuro! Lower Rank Three, Byōga! Lower Rank Six, Kamanué! Three... three demons in one!! Fused into a hideous monster, caw-!!!"
"What? Three Lower Ranks? That bastard Muzan has gone mad!" Sanemi Shinazugawa shot to his feet.
Though he was somewhat irritated by the woman, she had genuinely worked hard for the Demon Slayer Corps. As an outsider-or rather, a guest of the Corps-she had encountered the Twelve Kizuki on every one of the few missions she had undertaken.
Allowing a guest to fall into danger was a disgrace! An utter disgrace!
"Tell me exactly where she is! I'll head over right now!" Sanemi shouted anxiously.
"Lady Sapphire Star!! Single-handedly!! Slaughtered them completely! Reduced to ashes, caw-!!! Repeat! Lady Sapphire Star killed three Lower Rank demons-!!!"
"!!!"
Dead silence!
Absolute, suffocating silence!
Kagaya Ubuyashiki suddenly rose, moving so quickly that he knocked over the teacup beside him. Scalding tea spilled across the floor, but he didn't even notice.
His eyes, always filled with compassion for all things, now held tremendous shock and disbelief. The overwhelming news even left him briefly dizzy.
He gripped the low table before him with both hands, his knuckles whitening. His normally peaceful voice trembled with unprecedented intensity and solemnity.
"Rokuro... Byōga... Kamanué... three Lower Ranks... fused... into one?! ...Slain?! Can you... confirm it?!" His voice was urgent as he sought final confirmation. The news was simply too astonishing.
"Absolutely certain, caw!!!" The Kasugai Crow thumped its little chest and screeched with the last of its strength.
"I was observing nearby! The battle was brutal! The Jungle was devastated! The battlefield burned like purgatory! All three Kizuki were slain, caw-!!!" After shouting, the crow collapsed on the floor, exhausted and gasping for breath.
"Couldn't you damn crow have finished saying that sooner?!" Sanemi cursed, then dropped straight back into his seat.
The entire Council Chamber was so quiet that a pin could have been heard falling. The Kakushi members stood frozen, not even noticing the documents slipping from their hands.
In Sanemi's mind, all his previous vague impressions of that Foreign Huntress-
The enormous weapon that was less a sword than an instrument of slaughter, her almost outrageously brutal fighting style, and the irritating mystery surrounding her-all shattered beneath this thunderclap of a report.
Three! Not small fry! Three numbered Lower Rank Kizuki!
...And that... woman he'd secretly resented... had wiped them out... all by herself?!
Several seconds passed before Shinazugawa recovered a little of his senses from that soul-shattering shock.
The taut muscles of his cheeks twitched unnaturally. A short, heavy sound escaped uncontrollably through his tightly pressed lips.
"...Hah!!!"
"Three... in one... it seems Muzan's plans have advanced another step..." Even the bandaged face of the Serpent Hashira, Obanai Iguro, showed profound gravity. He was clearly thinking rapidly through the terrifying implications and Muzan's movements.
More than the news of the Lower Ranks' defeat, Obanai cared about this supposed fusion. Did it mean Muzan could mass-produce stronger fighters by merging weak little demons...?
Outside Tsutaya Village.
Carrying the Lower Rank head, pinned motionless by a Nergigante spike and no longer emitting demonic aura, the Sapphire Star met up with Hikigusa at the village entrance.
"Lady Sapphire Star! Are... are you hurt?" Hikigusa was slightly out of breath. Clearly, Hikigusa had already sensed her encounter with three Lower Ranks, but seeing her completely unscathed was still a shock.
"Relax, relax!" The Sapphire Star waved dismissively.
"Those three small fry, hurt me? They weren't even worth activating red sharpness for, hahahahaha! Let's hurry back to headquarters. We need to report to the Master."
"Yes!"
Before long, the two raced back to headquarters. The Hashira had already left for their respective territories; only Oyakata-sama remained, waiting in a quiet room.
The moment they entered-
"Lady Sapphire Star!" Kagaya Ubuyashiki could barely contain his excitement. He braced both hands on the table, trying to rise.
"To slay three Lower Ranks in succession... such a feat is truly..."
"You're too kind, Master. Please, sit down." The Sapphire Star hurried over to steady Ubuyashiki.
"I don't think killing them is all that impressive, so I brought them back..."
The Sapphire Star set the bundle of heads on the floor with a thud. The black-and-red sheen of Nergigante's spikes flickered faintly through the wyvern hide.
"Rest assured, Master. I sealed these things with Nergigante's spikes. Their demonic aura is completely locked down, so there's absolutely no risk of being tracked. Keeping them should be more useful than turning them to ash, right? Maybe we can learn more about demons this way?"
"Nergigante?" Ubuyashiki looked thoughtful. Since the Sapphire Star had entered headquarters, not a single swordsman had detected the demons' presence or scent. Indeed, not a trace of demonic aura had escaped.
"Yes, an Elder Dragon that used to pester me back home. With its absurdly terrifying regeneration and attack power, it chased me all across the New World, right to the ends of the earth..." The Sapphire Star rubbed her forehead. Even now, remembering Nergigante made the corner of her mouth twitch.
"Its spikes possess tremendous regenerative power and elderseal. They couldn't be better suited to suppressing demonic regeneration."
Oyakata-sama's gaze swept over the spike radiating a savage presence, and he considered it for a moment.
"You have thought of everything. But... perhaps we should give this to Tanjiro. It may... prove very useful to him."
The Sapphire Star raised an eyebrow but asked no further questions. "Give it to Tanjiro, huh... sure. Is the kid at the Butterfly Mansion?"
"He is," Oyakata-sama said with feeling.
"You have brought the Demon Slayer Corps so many... entirely new possibilities. Every one of us is deeply grateful!"
Ubuyashiki recalled when the Sapphire Star had first arrived-
The sight of stretchers being carried into the Butterfly Mansion in an almost unbroken stream, and the thick, lingering smell of blood mingled with medicinal herbs.
The wounded were in far worse condition than she had imagined-severed limbs, gashes deep enough to expose bone, damaged organs... relying solely on the Demon Slayer Corps' existing traditional methods of stopping bleeding and herbal treatments, recovery was slow and mortality was extremely high.
Unable to bear the sight, the hunter from another world had unhesitatingly brought out piles of Mega Potions, Nutrients, Rations, and even several precious Max Potions to distribute.
These refined medicines from the New World Elder Dragon Observation Bureau produced immediate results.
Wounds deep enough to expose bone swiftly closed and stopped bleeding after Herbal Medicine was applied. Even critically wounded patients could cling to life long enough to survive surgery after being given a Potion.
Yet even the most abundant stockpile could not withstand such consumption. The war between the Demon Slayer Corps and the demons had dragged on for years, with staggering casualties. Though the Sapphire Star did not mind at all, the Corps' members felt ashamed to use up their honored guest's rare medicines at such a rate.
Later, the Insect Hashira, Shinobu Kocho, offered to help.
Shinobu's laboratory was always filled with the distinctive scents of various medicinal herbs and the faint sounds of experimental equipment at work.
When she heard the Sapphire Star's idea, the eyes of this seemingly delicate yet resilient Hashira lit up.
"You mean... trying to grow medicinal herbs from your world here?"
"Exactly. Luckily, I brought plenty of seeds!"
The Sapphire Star carefully took several small packets made of an unusual material from deep inside her pack. They contained seeds of various plants she had specifically collected before setting out.
The two women got to work immediately, setting aside an experimental plot at the Butterfly Mansion. Kakushi members skilled in farming were also brought in to help.
The results, however, were mixed.
The problem lay in the soil itself.
The New World's medicinal herbs, especially those with powerful healing properties, depended on more than sunlight and water. They were deeply rooted in land repeatedly swept by Elder Dragon power and nourished by the energy of the dragon veins.
Although the soil here was fertile, it lacked that fundamental, vibrant "life energy," as though it were rich earth stripped of its soul.
In the end, only the most basic Herbs stubbornly took root.
They barely managed to sprout and grow, but their leaves were far duller than those of their counterparts in the New World, and their active ingredients were greatly diminished.
The Antidote Herbs failed to sprout at all. The Mandragora seeds did germinate, but produced only a few sickly leaves, never developing their distinctive rootlike fruit.
"Ah... they just can't adapt to this place." Holding a locally grown Herb leaf between her fingers, the Sapphire Star worked alongside Shinobu at the makeshift pharmaceutical equipment.
"Anything we make with these is probably going to be a lot weaker."
After repeated trials and adjustments to the formula, they successfully brewed their first batch of locally made "Potions."
Their effects fell far short of those the Sapphire Star had brought-
Drinking one did not produce that intense comfort of a warm current flowing through the entire body. It felt more like taking a potent herbal decoction that promoted circulation and cleared stagnant blood.
But its effects were undeniable: it could rapidly restore a great deal of stamina, accelerate wound healing, and stop bleeding effectively.
"It is enough. This is more than enough!" Upon learning of their success, the Master's voice trembled with a rare excitement.
"To keep the wounded alive and buy time for further treatment is already a heaven-sent blessing for our Demon Slayer Corps!" With the horrific injuries inflicted by demons, many swordsmen who would otherwise have died before dawn managed to pull through thanks to a dose of this medicine.
And so, producing these "weaker Potions" became one of the Butterfly Mansion's most important duties aside from treating the wounded.
Although a single dose could not restore someone on the brink of death as the originals could, anyone who had not died on the spot had a vastly better chance of survival after drinking one, giving the Corps' swordsmen a powerful lifeline.
When all nine Hashira gathered, the Sapphire Star solemnly placed an Ancient Potion in each of their hands-nine pills the size of longan fruit, with what looked like living flames swirling within them.
This included the habitually detached Mist Hashira, Muichiro, and the taciturn Serpent Hashira, Obanai Iguro.
"These are called Ancient Potions." The Sapphire Star's gaze passed over each Hashira.
"Back where I come from, they're miraculous medicines that can instantly bring a dying hunter back to peak condition. But their power... might be too much for you."
She paused, lowering her voice.
"For your bodies, taking one can only have two outcomes. Either you'll be reborn like a phoenix, with every injury healed and your stamina fully restored, even your fatigue swept away... or your body won't withstand the shock and will rupture from the inside."
"Do not use one unless you're truly at death's door! It can give you a second life! And don't chew them like candy! I'm talking to you, Mr. Muichiro. Please make sure you remember!"
Even Sanemi Shinazugawa, the most hot-tempered of them all, merely clenched the pill containing unimaginable energy in his hand and nodded gravely.
Gyomei Himejima shed tears of gratitude and compassion, chanting the Buddha's name.
They all understood that this was not merely power the Sapphire Star had brought them. It was also a weighty responsibility, a gift that staked everything on their chance of surviving when pushed to their limits.
She paused. "Sorry. I can't grow the high-grade stuff here. Only ordinary Herbs seem to do all right... if only we could grow more ingredients."
"This is already an immense blessing!" Oyakata-sama said solemnly. "Everyone in the Demon Slayer Corps is deeply grateful!"
The recollection ended.
Oyakata-sama touched his cheek. The Sapphire Star had also supplied him with many medicinal ingredients: Antidote Herbs, Blue Mushrooms, Spirit Deer Antlers, Honey, and more...
After he took these medicines from another world, even the curse rooted in his bloodline had eased considerably. Though his body remained frail, his vitality had grown much stronger, granting him more life and energy to fight the Ubuyashiki Family's sole stain-Muzan Kibutsuji.
"No need to thank me, Master. I'll go find Tanjiro now."
The Sapphire Star hoisted the sealed head onto her shoulder and strode out of the quiet room, heading straight for the Butterfly Mansion.
Watching the hunter from another world recede into the distance, Ubuyashiki bowed deeply.
Before you continue