Archive of Our Own

Chapter Text

The weight was always heavy. 

It was no secret to the members of the Demon Slayer Corps that the pillars were the backbone of the organization. An ordinary demon slayer could spark a sliver of hope, but a Hashira would set hearts ablaze. In their presence, all were reassured, as if the battle had already been won. The elite few revered by all, saviors of the millions, and aces of Ubuyashiki. 

 At least, that was the case for most hashiras. 

The soon-to-be-appointed Hashira may be the outlier: Insect Hashira, Shinobu Kocho. Like the fact that the Hashiras’ immense strength was known, so was Shinobu’s lack of it. This has been the buzzing gossip amongst slayers alike, especially the lower-ranked ones. 

In a way, it was ironic to have a pillar physically weaker than most slayers; the notion bred an air of envy that circulated the corps. The rumor mill’s whispers ranged from alleged nepotism to a disgusting allegation of an affair with a hashira to improve her standing. All the baseless and obscure nonsense never failed to pop veins out of Shinobu Kocho’s face. 

It was stressful enough that the Butterfly Mansion had recently received an influx of slayers; to add insult to injury, the kakushis were understaffed, leaving the mansion acting beyond its capacity. Even with all hands on deck, including Shinobu’s adopted girls, they had to fight tooth and nail to keep the mansion afloat.

Today was supposedly a big day for Shinobu. However, with the number of slayers in dire need of care, there was nothing to celebrate.

During Shinobu’s morning rounds, a kakushi had hesitantly approached her to inform her that a hashira had recently sustained a serious injury. Shinobu dropped everything to redirect instructions for the kakushi before making her way to a private room reserved for Hashiras.

 As she stood on the opposite side of his room’s door, her hand trembled as it made contact with the knob. The head of the mansion was not only tasked to maintain its efficiency, specialize in more complex and critical conditions, and most importantly, act as the private physician of the Hashiras. 

‘There’s a first for everything.’ 

She huffed sharply, and a smile appeared as soon as the door opened to reveal her patient. 

“Good morning, Tomioka-sama.” 

The taciturn pillar sat in bed, his bare chest basking in the warmth of the summer sun. His mind wandered into the window until the sound of her voice called for his gaze. His face was as bland as a cloudy day. 

‘Right, not much of a talker.’ A calm morning on the outside, a nervous storm within. 

“May I assess you?” She smiled, to which he merely nodded.

The laceration on his arm lay like a crack in the road. It was deep enough to penetrate through his haori and uniform, much less the top layer of his skin. From his bicep to his forearm, a trail of inflamed tissue surrounds it.

“Quite the wound you’ve acquired, Tomioka-sama. Were you dozing off?” Shinobu teases, latex gloves slapping into place. 

‘Who says that?!’ She cleared her throat.

His gaze remained unfocused on the drapes of the windows.

“Do you know if the demon who injured you used poison on you?”  She asked. 

He shook his head.

She nods, peeling the torn sleeve away, then unbuttoning the tattered uniform clinging to him.

“What was the mechanism of injury?” She asks. Her hands are soaking up a white rag. 

“Demon attack.” He responds bluntly, eyes shut. 

‘What would Kanae do?’ 

“Well, yes, but how exactly? A blade? Claws, poisonous claws?” Shinobu huffs. 

“…claws.” He murmurs. 

Shinobu tried to strike up a conversation while she assessed his injury. But she was met by an awkward silence and subtle nods from him. Giyuu’s lack of interaction did irk the woman, but because he was cooperative with her more relevant questions, he was able to slide under the rug.

Rather than attempt to drag out the interaction, she worked fast. When he didn’t wince at the ointments she applied to his skin, she raised an eyebrow. Despite the awkward tension, his lack of eye contact lifted a bit of weight off her shoulders.

She lets him out with a bandaged arm and a note to rest and come back for a check-up. A note which he so graciously left on the nightstand of her ward. Luckily for him, her rush to make it to her ceremony took him to the backseat of her priorities. 

She barely made it on time to the mansion that morning. Especially as bugs in her stomach clawed from within.

The Ubuyashiki Estate was serene––the cool breeze brushed past the swordsmen, and the soft song of the early birds played. Yet, amidst the calmness, a storm has been brewing within the newest hashira, leaving her petite body rigid. 

She was in the presence of the four strongest men in the Demon Slayer Corps. Himejima. Shinazugawa. Tomioka. Uzui. From her safe distance, she could feel their prowess and unwavering strength in every cell. All four decorated in their own right, possessing a capacity unattainable by many, surpassing her in every criterion.

 So naturally, Shinobu had every right to be nervous.

“Shinobu Kocho,” The master calls, “Today marks a momentous occasion. As you have slain your 50th demon as a Kinoe, you have not only shown immense strength and dedication to the corps, but unlocked the accomplishment of Hashira…” 

‘Strength without ever beheading a demon.’

 “A feat no man or woman can easily accomplish. To be a hashira is more than strength—it is an unyielding dedication to humanity: to protect and serve the weak….”

‘Almost as if he savors the word ‘weak’ before me.’

“Welcome, Insect Hashira: Shinobu Kocho.” The master announces with a reverent smile. 

The light barely reaches past the blinds of the estate. 

“I am reassured by your capabilities. Insect Hashira Shinobu Kocho, we eagerly anticipate your endeavors.” The kind master hush-spoke, a serene smile gracing his lips.

It melted the tension in her body, his kindness a soothing balm.

A kakushi arrived with folded garments for her. He bows to them all before placing the neat stack before her. 

All eyes lay on her.

They tried to crawl back into her throat. 

The uniform was midnight black, tinted with hints of purple, much like the one she had on. However, its buttons are adorned with the regal color of gold instead of silver. 

Her stomach finally drops to the floor of the estate. 

‘Only the immature cannot control their emotions.’

But the wells were too dry to dare let a tear escape her hollow violets. 

As she kneels before it, she feels Gyomei’s pitying eyes boring into her head. 

Perhaps even Ubuyashiki could see it, too, even without his full vision. 

Almost as if he knew how wrong it was for her to be here. 

“Congratulations, Kocho! How flamboyant of you to rise to the occasion!” Tengen, the loudest of the hashiras, beamed. His voice boomed as always, rattling birds out of their nests.

The old Shinobu would have furrowed her eyebrows immediately, then scolded him for his loud volume. Instead, she bowed.

Despite the obnoxiousness of his persona, his enthusiasm was greeted with subtle nods and silence from the three other hashiras. Neither Shinazugawa, Tomioka, nor Gyomei could fill the void of the excruciatingly awkward meeting, withholding their words as they always did. 

“Thank you, Uzui-san, and my fellow pillars. I intend to serve the corps with the utmost dignity as a pillar.” The lone woman strained a polite smile, remaining steadfast as she knelt with her colleagues before the Master.

When Kanae died, it wasn’t just her last family member who died. In that grave rested the Flower Hashira and the Head of the Butterfly Estate, too. Kanae didn’t just pierce through what remained of Shinobu’s heart; she left a hole in the Demon Slayer Corps. So, someone had to fill her place.

Finalization was little fanfare–it all rested on Shinobu’s shoulders now. Her small shoulders. 

Insect Hashira Shinobu Kocho. What a joke. 

Sanemi’s calm mask was fraying away from crumbling. 

Gyomei’s solemn tears make Shinobu’s skin crawl. 

‘I don’t need your pity.’

Aside from a set of new gold-buttoned uniforms, not much had changed. The gossip was as insidious as ever.

A few hushed whispers here and there during passing time. Harmless in nature, yet true in principle. She saw it in the darkened eyes of boys and the silence from the women who welcomed her. 

The first month of her new duties was uneventful, aside from the increase in workload and generous salary. Shinobu patrolled what used to be Kanae’s territory, she took on advanced assignments, and she ran the Butterfly Estate efficiently. The only difference was the darker abyss plaguing her heart, the absence of peace—of someone.

It still hurt to think about Kanae, so she drowned herself, mission after mission, and tended to the smallest of injuries.

Shinazugawa tried to scold him by stealing missions off her plate and wasting her time with his injuries. Just like he had done when Shinobu evaded sleep to care for patients after Kanae-

Shinobu brushed him off more easily than before. 

Tengen commended her as a “beast” at her craft. But all she was becoming was a monster.

Every time her blade would pierce through a demon, she would watch the dreadful vermin melt away, to bleed and wail in agony. Their suffering made her feel something—a fleeting satisfaction that fueled the flames within her. 

The thrill was a powerful driving force. After every mission, she would experiment more to enhance her poisons and techniques. Crossbreeding wisteria flowers here and there, and altering the poison to increase its potency. Eventually, she created stronger variants of her wisteria poison by mixing in doses of other flowers. 

Then one night, a stroke of genius finds her in the form of a precarious man during one of her missions. Half-dressed with his yukata hanging on by a thread, he was a stumbling mess as he embraced a jar of paste by a brothel. 

She tried to scurry past him, eager for a day’s rest from a night of battle. Until she saw the lack of a bottle of sake and his glassy eyes. 

‘An opium smuggler out in the open. Even with recent regulations, it remains rampant.’

He had minutes before he would succumb. 

She almost reaches out to him, but the lack of an antidote forces her to move along instead. 

She had seen suffering before, but somehow hadn’t reached the point of numbness. If only he were a demon. Shinobu wouldn’t feel a tug on her heart. 

Her heart skips a beat at the thought. Her sharp eyes spare him a final look, then the jug he clutches onto. 

Shinobu was no longer the helpless girl who hid away in the arms of Kanae. 

She was no longer Shinobu at all. 

So began her descent.

Chapter Text

Years had passed, but the memory of her late sister always reared its ugly head. Kanae lingered in Shinobu’s slumber. Sometimes, Shinobu would hear her voice in the hall of the Butterfly Mansion—until she’d meet a deafening silence. 

Nights of waking up in a pool of sweat often ended in her sanctuary.  In the arms of her pestle and mortar, she would crush herbs for tea. The concoction itself seldom calmed her or helped her get back to sleep. Instead, the sensation of grinding matter against the mortar’s stone walls became an outlet. 

That got boring too quickly. 

The moment the last clump was smushed into dust, the ache in her heart would come back as fast as it had left.

One night, she gave up on rest altogether. 

After dinners with her sisters, she would pretend to slip away into her quarters. When the last of the lamps had been blown out, she would glide down to the lab. In the beginning, her escapes were discreet. Her overactive mind was better off working away, reviewing patient charts or compounding new poisons. 

‘What better use of energy is there than work?’ She chuckled. The bags beneath her eyes merely doubled.

Lately, she had been interested in an entirely new type of study. This new compound was sealed away in a porcelain jar, hiding beneath a fabric embracing it. Aoi did not ask what it was. The young girl understood her master owed her no explanation. Not even when Shinobu had arrived home with it, dressed in a dark cloak late at night. 

Shinobu scooped the small jar with both hands, carrying it to the laboratory attached to her office. She carefully set it on one of the cleared counters. When she lifted the delicate lid on top, her nose scrunched at its latex smell. Although it was far from enough to deter her. She had already gone through the trials to acquire it. Most notably, running through the shadows of the red light district.

‘This is for a good cause.’

With a spatula, she scooped a calculated amount of the brown paste onto an empty mortar, gradually pouring in bits of fine wisteria powder.

What would her father say if he saw her with this? 

Her hand froze midair at the sudden thought.

‘..he would be proud of me for indulging in my curiosities. He always said-’

She blinked. What was it that he always said?

The more she chased after the memory, the fuzzier it became. 

‘Let your curiosity run wild? Follow your brain? Curiosity is the soul?-’

‘Focus, Shinobu.’

It wasn’t like she committed a crime for fun. She genuinely needed it to help with the greater good of humanity. If proven right, the world would become a better place! If anything, had she truly committed a crime?

Her left eye twitched. 

After a few minutes of work, the paste had become a uniform mixture. As she allowed it to sit, she boiled a solvent in a flask. 

‘If I just get this right…things will be better…’

When the gas bubbles began to evaporate from the flask, she allowed it to rest. She meticulously documented each step in her journal while she waited for it to cool down. 

—Journal entry—

‘Opium to wisteria powder to solvent ratio…1:1:10…’

‘Hypothesis:...the addition of opium to wisteria poison will have a sedative effect that can weaken demons. When injected…’ her hand faltered at the thoughts formulating in her mind... 

Her lips nearly curved upwards. 

‘...the opium will induce excruciating pain, a severe neurological response to the demon's sensory system, overwhelming neurological and sensory processing in battle. Hopefully, it weakens their BDA. This effect would aid in the wisteria, rendering their bodies too weak sleepy groggy to attack the poison. Opium = sedative. Wisteria = poison. ‘

She shut the book carefully.

The image of a demon clutching its chest suddenly consumed her. 

Out of nowhere, the mundane task of gradually mixing the paste sent a rush of adrenaline through her body. 

She could almost hear the screams of agony. 

Somehow, it brought life into her hollow eyes. 

Her late-night sessions went from secret escapes to a nightly routine. 

Aoi and Kanao eventually caught on. 

“Shinobu-sama?” Aoi, the young girl with pigtails, waved a hand at Shinobu’s face, snapping her away from her trance. “Do you not like the food I made?” Shinobu was met with ten pairs of eyes looking at her with concern at Aoi’s voice.

“Of course I do. This meal is lovely,” Shinobu cracked a smile, taking a bite of the Tsukudani Ginger prepared by Aoi. “Mhmmm, your cooking has greatly improved, Aoi.” She hummed softly, bringing a smile of relief to the faces of the little girls at the table, especially the chef. 

“You need to take care of yourself, Shinobu-sama.” Aoi frowned, continuing to eat her meal. 

The young girl had the highest respect for her mentor since the Kocho sisters took her in, so naturally, she was worried for Shinobu. The feeling was mutual among all five of the Kocho sisters’ adopted sisters. 

Shinobu chuckled softly, her shoulders slightly shaking, “I am taking care of myself, I promise.” She set her bowl down, her eyes unconsciously drifting to the mat her older sister used to sit on. “I have just been busy with missions and my patients. So I have found my mind wandering off at times.” 

She gazed back at them, her eyes full of a familiar warmth. “Thank you all for your help, I wouldn’t be able to run the estate smoothly without my best assistants.” She clasped her hands together in a small cheer, lifting the spirits of her little sisters, even earning claps and cheers from the trio. 

But it wasn't enough to undo the knot in Aoi’s stomach.

“Shinobu-sama, how was your mission last night?” Naho pried.

“Did you sleep immediately after you got home?” Kiyo chimed in.

“Was Tomioka-sama a good partner?” Sumi huffed.

“It was quite a long night, but the mission ended without a hitch. Yes, I immediately went to sleep. Thanks to the wonderful bed you girls set up,” she responded, keeping her heavy eyes wide, “Yes, he was a good partner.” She strained slightly.

That was enough for them to hear.

It was a pleasant night for once; the ache in her chest and the knots in her gut were lost. Within these wisteria-guarded walls, their sisterhood gave a semblance of peace. Instead of going to prepare for bed, the trio insisted on braiding each other's hair, much to the reluctance of the older girls.

 Ultimately, the trio’s charms had their way; by the end of an hour, all the girls’ hair was woven together, twisted to make updos, and adorned with various flowers. The trio, proud of their work, paraded their hair in front of an audience. As expected, they were well received.

Eventually, Shinobu had to be the bearer of bad news, sending them all off to prepare and sleep. Although the decision brought great disappointment, they did as told, with Aoi breathing a sigh of relief. As Shinobu was preparing to retire for the night, she noticed a small figure standing next to the shoji door, its head hung low. 

“Kanao? What are you doing here?” Shinobu paused to look at the young girl. 

Kanao’s hair was still woven into an intricate design, and sweat beaded across her face. Silence filled the halls, and the sound of a faint gust of wind was louder than the young girl’s breathing. 

Shinobu wasn’t going to lie. She yearned for the warmth of her bed. So, her patience was shorter than usual, a sigh fighting to release itself. She was about to try to make Kanao speak, until she heard the sound of a coin flipping. 

PING

CLINK

Heads.

Kanao lifted her face to meet Shinobu’s eyes, a pitiful look crossing her face. “I…” Kanao stuttered, pointing to the sheathed blade attached to her hip, before pointing back to herself. 

Oh. 

Any semblance of a smile vanished on Shinobu’s lips. “No, it’s too dangerous.” The young Hashira was not going to have it; she needed rest, not this. 

Before she could part ways, Shinobu was met with a soft thud on the floor. Kanao bowed deeply, her forehead against the wooden floor. Kanao’s small form shook within her pink kimono, with more beads of sweat escaping her. Shinobu so badly wanted to say no, to refuse Kanao. The Pillar needed to do what she should have done to Kanae, to stop her from ever wielding a damn nichirin blade. 

Forgotten was the smile Shinobu tried so hard to keep. The air was thick; neither one could break through it. Shinobu’s lips parted momentarily, yet unable to utter a sound––instead of Kanao, she saw her beloved sister. 

Damn it.

She shut her eyes tight before a lump could form in her throat. Hoping it would snap her out of it, before she could do anything immature, or a tear could escape her. When her eyes looked again, it was finally Kanao. Even after a moment passed, Kanao remained firm, dissolving her master’s firm resolve into nothing but a whim. 

Kanao never asked for a dime, never a favor, even when she knew her sisters would comply regardless of what she wanted. The Kochos had always prayed for the day Kanao would finally break free of the repression within—to find her voice. But never like this. Of everything, Kanao had to ask Shinobu to send her to an early grave. 

“Kanao, no. Never ask me this again,” Shinobu’s voice was strained, feeling the monster within her clacking against its shackles. She had to get away; she needed to run away before something could snap, but a pair of moist hands hooked onto her ankles. 

“M-m-master…” Kanao gasped, her grip shaking.

Shinobu never looked at her. She needed to remain adamant, even when every fiber in her body rebelled against her mind. All Shinobu wanted to do was protect her girls and what they had left.

But the sight of the pink butterfly on her hair was nearly enough to shatter Shinobu. 

She swallowed a lump in her throat. Her protests died long before her lips parted.

There was the young girl Shinobu had bathed the dirt off. The same one she had purchased to set her free.

‘Why must you make things harder for me?!’

 “...Fine. I will train you.” Shinobu shuddered, finally looking back at Kanao’s delicate face, “On the condition that I will teach you for the sake of self-defense. You will not partake in the final selection or become a slayer. Understand?” 

Kanao wanted more, but for this time, it was more than enough. The younger girl could only mumble a thank you before running off to bed in an awkward stride. For once, Shinobu saw something in Kanao, a flickering light in her eyes––life.

It was almost strong enough to eat away her regret. 

Farewell to any semblance of sleep, then. She tossed and turned the entire night––too cold, too warm, too bright, too much. 

‘What would Kanae have done? Kanao’s happiness without a doubt.’ She yawned. 

Shinobu could almost feel Kanae’s chastising eyes upon her. 

‘Happiness at the cost of a life put at risk? Or happiness from a fulfilled life?’ She stiffened. ‘What more could Kanao want? She can be with Aoi and the girls, play in the sun, do chores, blissful ignorance-’

She bolted upright in the cotton futon. What an insolent thing to say about the girls from different mothers whose lives had been shattered like hers. 

Who was she to deny Kanao? When she had already gone against Kanae’s dying wishes.

‘…we’re not so different…’

–

Shinobu never understood the saying “cursed with knowledge.” 

Growing up gifted with incredible intelligence felt like a superpower. While her peers struggled with words and numbers, she could recite paragraphs and solve equations. 

It wasn’t until ‘adulthood’ that she realized what it meant.

Kanao didn’t need training from her. Her small hands naturally wielded the wooden blade she was given. Her body rotated with practiced balance when she performed her second form. Neither her wooden nor real blade shattered from the delicate twist of her Crimson Hanagoromo attack.

Kanao obviously watched the Kocho sisters spar enough to know how to fight. 

It felt uncanny to teach Kanao Flower Breathing when she seemed to breathe its art already. In fact, it was ironic for Shinobu to teach Kanao techniques she couldn’t even accomplish. The thick stacks of bamboo—meant to simulate a demon’s head—which Shinobu had yet to decapitate, were dismembered in weeks by Kanao.

Which made it all the more terrifying.

Each milestone was just a step closer to death’s door.

Shinobu’s heart swelled whenever she watched Kanao train in the sweltering heat of the sun. 

The butterfly in her hair never failed to make her heart race.

Despite Kanao’s raw talent, Shinobu never appointed her as tsuguko. She would train Kanao when her busy schedule deemed it appropriate. By day, Kanao would complete the chores of the Butterfly mansion, then train during her spare time. At night, she would sleep soundly in the comfort of her cotton futon, gazing out the window whenever her Master headed out for a mission.

Kanao would never say it, but the beads on her forehead watched over Shinobu. Because no matter how many times Shinobu left for missions, the fragility of life was ever-so-present. That was Kanao’s life.

Even when Kanao’s work in the mansion was lackluster at best, and patients often got worse under her care, Shinobu still never gave in. 

Especially not after her tsuguko’s Yuna and Nina were- 

CLASH 

The sound breaks through her wandering mind.

SCHLICK

THUMP

She froze.