Morning sunlight filtered through the window lattice, spilling gently into the quiet, tatami-floored room.
Kagaya Ubuyashiki sat upright in the seat of honor, his expression as peaceful as ever, though a barely perceptible trace of concern lingered between his brows.
The Sapphire Star sat cross-legged opposite him, having changed into a clean set of hunter's underclothes.
"Sapphire Star." Ubuyashiki's voice remained gentle, carrying sincere regret.
"Regarding last night, Sanemi acted far too rashly. He disturbed your training and nearly caused a disaster. As Oyakata-sama, I failed to restrain my subordinate in time. The fault is mine. Please accept my sincere apology on his behalf." He bowed slightly.
The Sapphire Star hurriedly waved her hands, looking a little embarrassed. "Master, please! You really don't need to apologize! Actually... I ought to thank the Wind Hashira."
"Oh?" Ubuyashiki raised his brows slightly, a hint of amusement in his eyes.
"Yes!" The Sapphire Star nodded emphatically. "Though the process was... uh, a little intense."
Remembering the Wind Hashira's teeth-baring grimace, her mouth twitched.
"But those pointers he gave me really opened my eyes!"
She gestured, trying hard to explain herself. "He was right. The way I practiced my Breathing Style, and the way I fought, was too crude! All I thought about was blasting my power out and piling more force into my attacks. It was like... hmm..." She gave a self-deprecating laugh.
"Then I am glad." Ubuyashiki nodded with relief.
"Though Sanemi has a fierce temper, as the Wind Hashira, he does possess unique insights into controlling breath and strength. If those insights proved useful to you, there could be no better outcome."
He changed the subject, his tone gently inquisitive.
"Sapphire Star, by blending the fundamental principles of Breathing Styles so perfectly with your own tremendous power, you have already forged a path that belongs to you alone. Have you perhaps... thought of a name for this new power, which unites strength from another world with the art of breathing?"
"A name?" The Sapphire Star paused, then scratched her head sheepishly.
"Well... I really haven't thought about it." She looked candidly at Ubuyashiki.
"Master, honestly, I feel more like I've incorporated the precise control of Breathing Styles into the way I already fight."
The Sapphire Star spread her hands. "So I don't think that counts as inventing a new Breathing Style, does it? It's just... refining how I release my power? I'd feel embarrassed giving it a name."
Of course, she was putting on an act. She had already thought up eight hundred names.
Dragon Breathing, Sapphire Star Breathing, Long Sword Breathing, Ripple Breathing...
Kagaya Ubuyashiki chuckled softly at her words. "Sapphire Star, you are far too modest. To blend another world's tremendous power so seamlessly with this world's art of breathing, making external strength your own, is itself an extraordinary creation. Rather than confining yourself to 'forms,' you have reached directly for the essence of how power is used. Perhaps... that is precisely what makes your strength unique."
"There is no need to rush into choosing a name. Once your power becomes more harmonious and your understanding deepens, inspiration may come naturally."
Ubuyashiki paused, his tone growing even gentler and more considerate. "Also, if you need to practice, there is no need to venture alone into remote mountains again. Headquarters' training grounds are always open to you. There, you may not only practice in peace, but perhaps exchange pointers with our members whenever the mood strikes you. Comparing your approaches might offer further inspiration."
His offer was meant both to make things easier for her and to help her settle more naturally into the Demon Slayer Corps, avoiding unnecessary misunderstandings and conflicts like those of the previous night.
"Really? That's wonderful! Thank you, Master!" She immediately nodded in agreement.
"Having training grounds will make things so much easier! I'll be sure to... uh, control my strength!"
Ubuyashiki nodded with a smile. "Of course. Hikigusa will arrange everything for you."
Leaving Oyakata-sama's quiet room, the Sapphire Star felt especially cheerful as the warm morning sunlight washed over her.
Not only had she found a place to train, but more importantly, her control over her power had improved again! That Wind Hashira might have been as hotheaded as a Rajang, but his advice... really did cut straight to the heart of the matter!
With the Fatalis blade over her shoulder, the Sapphire Star headed toward headquarters' training grounds with light steps, full of anticipation for the future...
Time slipped quietly by as she devoted herself to honing her skills. Life at Demon Slayer Corps Headquarters proved unexpectedly regular and fulfilling for the Sapphire Star.
During that time, Kasugai Crows arrived one after another with reports of demons wreaking havoc across the country, sometimes in remote villages, sometimes on the outskirts of towns.
Hikigusa occasionally mentioned vague intelligence about a Lower Rank being sighted somewhere, but Kagaya Ubuyashiki never sent the Sapphire Star to deal with it. He seemed more inclined to let this warrior from another world settle quietly and absorb the new system of power she had encountered.
Every day, the Sapphire Star traveled between her quarters and the training grounds, gradually weaving her understanding of the "precise control" and "flow of power" of Breathing Styles into her battle instincts, honed through countless trials.
Occasionally, bold Corps members approached her at the training grounds for a spar. Within a few exchanges, that massive blade, seemingly heavy and slow yet striking with overwhelming force, usually left them scrambling. Her parries, precise down to the smallest fraction (Clang!), and her sudden explosive thrusts always made them feel as though they were facing a moving mountain clad in ice armor.
That peaceful stretch of training was abruptly shattered one misty morning.
Like a shadow blending into the morning fog, Hikigusa appeared soundlessly before the Sapphire Star just as she was about to leave for the training grounds, wearing an expression of unprecedented gravity and urgency.
"Sapphire Star!" Hikigusa kept a low voice, but the urgency was unmistakable.
"Urgent orders from the Master! Please come with me immediately!"
The Sapphire Star stopped, her golden eyes sharpening at once. "What happened?"
"Mount Natagumo!" Hikigusa spoke rapidly.
"Overnight, we lost contact with every Kakushi member sent to the area, as well as three patrol squads of swordsmen! The last messages from the Kasugai Crows were chaotic. They mentioned 'puppets,' 'threads that can't be cut,' and 'monsters controlling corpses'... The situation is extremely strange and dangerous! Giyu Tomioka and Shinobu Kocho have already gone ahead! The Master orders you to reinforce them at once!"
Mount Natagumo! The name meant nothing to the Sapphire Star, but the urgent deployment of two Hashira-level fighters was enough to show how serious the situation was!
"Understood! Let's go!" Without a moment's hesitation, the Sapphire Star turned and went back to her room to grab her hunter's pack, which she always kept stocked with emergency Max Potions and whetstones.
She shouldered the Fatalis Demolisher resting against the wall. The sheath formed from frost glimmered coldly in the morning mist, and an ominous pressure instantly spread through the air.
Hikigusa immediately turned to lead the way, and the two left headquarters swiftly, like twin gusts of wind.
They raced onward, Hikigusa weaving along the forest paths ahead at astonishing speed.
The Sapphire Star followed close behind. Neither her massive frame nor her heavy weapon slowed her down. Every step was steady and powerful, yet landed without a sound, revealing how much her control over her strength had improved over these past few months. Her breathing was deep and sustained, drawing efficiently on the strength of her entire body as she ran, with barely any exertion.
The air ahead grew colder and damper, and the mist gradually thickened, carrying an unsettling odor of decaying vegetation mixed with a sickly sweet, bloody scent. At the edge of their vision appeared a mountain completely shrouded in dense white fog, its outline blurred and distorted. From a distance, it resembled an enormous pale spider crouched upon the earth.
It was Mount Natagumo!
Two figures were already waiting at the foot of the mountain.
One wore a butterfly-wing-patterned haori, her figure graceful and a warm, approachable smile on her face.
The other wore a haori with different patterns on either side. His handsome face was expressionless, and he exuded an aloofness that kept strangers at bay.
Seeing the Sapphire Star rushing toward them, Giyu Tomioka merely glanced over, his eyes calm and untroubled.
Shinobu Kocho inclined her head slightly. "Sapphire Star, you're here. The situation is worse than we expected... There's something strange about this fog."
The Sapphire Star stopped before them and looked toward the deathly still mountain.
No further explanation was needed. The nauseating, sweet scent of blood hanging in the air and the deathlike silence deep within the fog said enough.
"Do you two have a plan?" the Sapphire Star asked, looking at them.
Giyu Tomioka remained silent, gazing into the depths of the fog as though sensing something.
Shinobu Kocho glanced at Giyu, sighed softly, and explained.
"This fog is unusually thick. Visibility is extremely poor, and it severely interferes with our senses. Moreover, according to the last confused reports, the enemies on the mountain seem capable of controlling 'puppets'... Most likely... our fallen members. We'll cover more ground if the three of us split up. But be extremely careful. If you find any survivors or anything unusual, contact the others immediately with a signal flare."
She looked at the Sapphire Star and Giyu. "Sapphire Star, Mr. Giyu, what do you think?"
Giyu Tomioka finally spoke. "...Mm..." It counted as agreement.
The Sapphire Star nodded. "That works." Her gaze fixed on one direction.
"Then I'll go this way."
Shinobu Kocho nodded. "I'll take this way. Mr. Giyu, I'll leave the other side to you~" She pointed in another direction.
Giyu Tomioka gave no reply. His figure flickered, and he vanished soundlessly into the thick fog like ink dissolving in water, moving so quickly that he left only a blurred afterimage behind.
Shinobu Kocho also glided lightly into the dense mist in her chosen direction, silent as a butterfly flitting through flowers.
The Sapphire Star drew a deep breath of the cold air, heavy with that sickly sweet scent of blood, and tightened her grip on the hilt.
The light-devouring blade of the Fatalis Demolisher seemed to sense its wielder's fighting spirit and gave an exceptionally low hum. Without further hesitation, she strode forward like a moving fortress, entering the pale mountain forest shrouded in death and sinister threads.
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