The Trainer From Hell

Kasumi traveled long enough, occasionally stopping to buy what food she can.

She once tried to have Nezuko eat rice balls and swallow it, and tasting other food they can afford. But each taste, Nezuko would puke it back out.

The only thing she liked, was sashimi. Well, oni eat raw flesh...so Kasumi would often catch animals, bleed it away to clean it before letting Nezuko have it. Otherwise, she sleeps most of the time.

Problems solved, Kasumi can travel without worries.

She soon reached a way house about a week later...and dealt with their first tru-blu oni eating the other resting travelers it killed.

Kasumi's first test, was fighting this thing.

This thing was different from her sister.

The teeth, skin color, body proportions, all wrong!

'Perhaps if Nezuko ate humans, she'll end up like you...like, hell no!' Kasumi cried, using what she knew with her hatchet. 'Nezuko, he's perfect example we got here! You must absolutely refuse to become anything like him!' Nezuko looked at the repulsive sight before her even if her mouth and stomach said otherwise, vehemently shook her head and joined in on the fight, fighting like a primal beast.

From afar, Sakonji watched the two sisters fight their first demon.

There's something about Kasumi...

...the way she fights alone was eye-raising.

She treats her hatchet like a sword.

Her stances. Her attacks.

"Giyuu, this young lady already has an art. And you sent her to me to be a pupil of the Water Breath." he thought in a deadpan.

However!

Kasumi's physical abilities...horrible! She tires too easily! Or could it be because of her job? Looks like training and health issues are to be dealt with.

Charcoal Burners don't earn much money.

He can't do 'the usual' on Kasumi. He'll have to do both her health and her training. She'll understandably be behind, but still...

He's seen enough.

'It seems that to be a slayer...you really need to stop burning charcoal, girl.' he said as he killed the demon for the girls. 'Pollution is bad for health. Explains why all family heads don't live long and so will you even if you had a normal life as long as you keep that job up.'

'B-But what else can we do? It's our livelihood! Moreover who are you?!' Kasumi sputtered out.

'I'm Urokodaki.' that got the sisters stunned at the mention as Giyuu told them to find a man with that name. He found them first! 'And let's go to my home first, before we get talking.'

After a few days' of travel...Sakonji discovered just how Kasumi manages her changed sister and sees their interactions. For an Oni, the only thing that's physically changed was her eyes, teeth, and preference for raw flesh. However, if Nezuko ate humans, she would fully become Oni who's a danger to everyone and lose her own self-control even around her sister. Sashimi does nothing somehow while still sating her hunger and Kasumi diligently makes sure no blood remains. Otherwise if no food, Nezuko just sleeps.

Upon arrival in his home...

Kasumi was helpless. She collapsed on the floor, unable to move and red-faced.

'...looks like we got a lot of work to do.' Sakonji shook his head. 'Kasumi. If you will pursue the path of Demon Slaying, forget being a Charcoal Burner if it affects you this bad already.'

'W-what're you talking...about?' Kasumi gasped for air as if she just got air back after drowning.

Sakonji had to dumb down for two uneducated children the hazards of working with an occupation that eventually causes Lung Disease which was reason why Kamado family heads didn't live long lives from being poisoned by dirty smoke.

'Understand now, girls?'

Nezuko was horrified. Kasumi was shocked.

'Dad died...because of our job?' Kasumi shook. After she was born, their father had ten years afterward. In fact, when she was five, he was already bedridden!

'And you're well on your way if you don't stop.' said Sakonji grimly to the shaken sisters.

'...five years old. The first memory I kept was dad being bedridden already...' Kasumi mumbled. 'The family dance never saved him because he still tried to provide. Two more years I'll be just as sick too...'

'That is why right now, before you can even THINK of becoming a Slayer, we should purge you clean first.' said Sakonji. 'It's a tough path, but for health and finding as well as fighting for your sister's salvation, you'll do anything. Correct?'

'Yessir!' Kasumi swore. 'I'll do it!'

'Good. I'll handle Nezuko's fishy food, you work hard to heal yourself before you're beyond saving like your father. Doesn't help that you probably started at ten judging by the timeline I got...'

'Uhhh no, I just started last year...mom did the charcoal burning until she's confident I can do it.' said Kasumi. 'But she told me how quick dad got sick.'

'Ohhh good, you'll be a lot easier to heal then.' Kasumi beamed at Sakonji's verdict.

'Really?!'

'Its. Hard. Work.'

'I. Don't. Care.'

Nezuko looked at them as if hanebados were flying here and there.

'Well, you said it.'

xxx

After months of pure suffering...

'It's gonna be New Year's soon huh...' Kasumi mused as she saw the snow outside in their first new year away from home.

'Yes. You girls have been here for quite a long time now.' said Sakonji.

'Yeah...Nezuko and I had full stomachs for a change...we used to skip meals just so our younger siblings will grow up well.' said Kasumi, making Sakonji pause. 'Hanako, Shigeru and Rokuta need more food than three of us older ones did.'

"First pollution and now malnutrition?!" taking good care of family is good, but not at your own expense!

'Sensei, I'll have to do the dance at sunset, finishing at sunrise.' said Kasumi. 'Can I not get a beating for today?'

'The Dance of the Fire God, huh? I'm curious...but really, sunset to sunrise?' Sakonji asked, baffled.

'Yup. Dad made me watch. Sometimes the kids join in in watching. But its something only the family head should do. In this case, me.' said Kasumi. 'He taught me all 12 dances I must repeat with particular breathing methods...' that got Sakonji intrigued at those words. 'Come to think of it, Breath of Water's somewhat similar and not at the same time!'

'...I need to see how you breathe when you do that dance for me to make a verdict. So today I'm gonna let you have an off day. You go play snowball fight with Nezuko or something.' he chuckled. 'Before that...how did this begin exactly?'

'Humm...since I can't read, dad would tell me our history's beginning as a lesson.' said Kasumi cheerfully. 'It all began with Sumiyoshi, the first Kamado in history...back then, only nobles have surnames. Us poor folk don't, until laws changed later in the line...but nevermind that, back to Sumiyoshi! He was sixteen when he married his wife Suyako who was fourteen. They got money from their families to build the house our family lived in for generations. However, Sumiyoshi had no job and he thought of Charcoal Burning as family trade.'

'But one day at night, he and his wife got attacked by a murderous lunatic, and were saved by a swordsman, Tsugikuni Yoriichi.' Sakonji had to hold back his choke. 'He saved them from the lunatic and Sumiyoshi in turn offered him hospitality as gratitude and they became great friends. However, sometime later Yoriichi visits as a sad, somber person lately. So Sumiyoshi opened his home to him. Not much detail was there, but by the end of it, Yoriichi taught Sumiyoshi the Dance, and gave him his hanafuda earrings. The dance and the earrings became a Kamado Family Heirloom since because Yoriichi left the family after Sumiyoshi mastered the dance and breathing patterns, something about unfinished business.'

'There were times I wish there was more to that story...Sumiyoshi-san's a lazy writer.' Kasumi sighed. 'It's the Sengoku Era we're talking about! Its rare to meet a good samurai as samurai back then are self-serving assholes!' she complained. 'The next generation, his son Sumihiko was at least, very wordy so we had a clue what that era was like!'

"It's destiny." Sakonji thought as that man, was one of the first demon slayers in history. He was the first Breath of the Sun user, passed down his style on the sly to the Kamado Family with whom he was close friends with and now by deciphering the dance, they may know how it's done!

That night...Kasumi wore the traditional family costume, after setting up a ring of fire with tall torches.

'Not the facial veil Kasumi. I need to see how you breathe with that dance.' said Sakonji sternly.

'Eh? OK...' so Kasumi gave the veil to Nezuko.

'And are you seriously gonna dance barefoot?!'

'Tradition!' said Kasumi with a beaming smile. 'Besides, it never hurt us unlike normal...this dance might be frostbite-proof since dad and I never had frostbitten feet!' she swore confidently.

Soon when the sun fully set, the dance begun.

'Nezuko you watch too. Because if anything happens to Kasumi, you will inherit this too.' Sakonji instructed Nezuko who obeyed.

Kasumi repeated all 12 'dances' when in fact it's all freaking sword attacks!

Sakonji face-palmed. Just how naive, is this family? Well, at least the Progenitor Art isn't dead...

He respectfully waited until sunrise. By that time, Kasumi was understandably, exhausted and slept the whole day.

The irked old man wrote two letters and sent his crow off.

xxx

Next day...

'Kasumi, Nezuko.' Sakonji began as they were outside the house. 'Giyuu originally sent you to me to become my pupil, but as it stands, the swordsman slyly taught your family his sword style, the long lost Breath of the Sun, the progenitor of all Breath Styles known today.' he explained. 'He skillfully hid each technique in each twelve dance as in each dance, there are useless moves meant to conceal the weapon within. So instead of learning Water Breathing from me AFTER your physical training, we will decipher and master the Breath of the Sun, your inheritance before we get to the Water Breath.'

'Hai, sensei!'

With determination, they picked apart the twelve dances to uncover the hidden weapon within per dance.

Then they began giving it names that Kasumi decides, and Sakonji ordered her to do repetition training at full power alongside extremely harsh training for her to survive Final Selection.

And when Kasumi turned fifteen...

She now has a more feminine hairstyle. She now has bangs and fringes framing her face, and her hair in a high ponytail. She now wore a kosode-style yukata too with ankle strap sandals made of soft leather and rubber. The craftsmanship showing that it was a very crude attempt of imitating the western shoes that's an in, in a modernizing world. But so far, only big cities were 'going western'. Everywhere else in Japan still the same.

Sakonji told Kasumi that she no longer has to play the role of male. She must come back and embrace the lady she should have become as she is approaching marriageable age. And its now her turn to rely on men after shouldering everything for so long. Kasumi had no idea what 'that concept' even is, being a 'man' for so long, an exasperated old man had to hire an old granny to teach her part time in the mornings in their first year together, teaching her how girls should behave, talk, and other feminine arts on her first few months in rehabilitation. She also learned how to read and write. Just enough kanji needed in life.

In the mornings as after lunch, hell comes next. Sakonji was uttermost nasty in training.

And now at her second year, it just got worse, her reprieve being New Year's Eve for her dancing. He was harsh and strict because she's a girl, that she needs all she can get to survive!

It helps that Kasumi was diligent and constantly challenges herself, something Sakonji and the old granny appreciates. 'She would make a wonderful wife someday, Sakonji-san. She's also a wonderful Katemeshi and grilled fish cook(anything goes potage).' said the old granny Sae. 'Too bad she just can't comprehend it, living as a boy for so long.' she tut-tutted. 'How on earth is she raised, that she is a virtuous girl in everything but gender? I've never seen a child who's willing to go far for family when most kids we see these days think of themselves more than others.'

'Well, Kasumi had good parents and younger siblings...whom thieves took from her so I'm raising her in their stead.' in a way he's raising her to be a Slayer other than giving her what she should have had.

'Shame.'

And now at age 15, she mastered the two Breaths to Sakonji's satisfaction. She has technique, but needs more physical work.

Due to this, Sakonji could not bring himself to let Kasumi go to Final Selection for her own sake, but got her a Nichirintou anyway.

She's quite small due to malnutrition, standing at 5'0 for someone who's 15. She's wearing a pink-and-purple ensemble of a yukata and haori with wisteria flower prints and purple leggings. She also has spare clothes in possession as well as a spare pair of shoes. Her sword was also feminine in appearance with a purple sheath. Her hair has a pink ribbon holding it up. The girly ensemble was to remind Kasumi of what she is and what she should be, to 'wean her off' of living as a boy.

'Kasumi, due to our training focusing more on rehabilitation and technique, we paid the price through strength in return.' Sakonji told her. 'Therefore you will go next year, and spend this year physically training yourself in strength, speed, reflexes, and agility.' he instructed, giving her a scroll. 'However, you are still duty-bound to kill any monster you see with your blade. If anything happens, send me a letter, alright?'

'Alright.' Kasumi nodded. 'Nezuko and I are off now, sensei!' Kasumi bid Sakonji goodbye, while carrying Nezuko in a crafted wooden backpack box.

"Take good care girls...for right now, you are just by yourselves." Sakonji in good conscience, could not send Kasumi alone to Final Selection due to lacking in power. He made up for it by making her master Full Focused Breathing, Technique Mastery, Battle Tactics and Strategy while sparring with him, Survival Skills Training, and Basic Education...and Evasion Training in trap-riddled Mt. Sagiri just so she'll survive all her fights other than win.

So now, this training, is for pure physicals, while breaking out of the tiny world Kasumi and Nezuko were confined to. They must see the world. Who knows? Maybe they'll find a husband along the way. Nezuko's state notwithstanding.