Year 782; Heian Period, Nihon.

The night is black amongst the roads of a long, sprawling city. Everybody has practically crashed into slumber except for a few sporadic crowds that have more unusual activities to lead. Included among them is a man who sits by candlelight at a maple woodland counter, jotting down several wrapped paper notes to a leather diary in a hunched manner. His eyes were squinted; and the only tone away from the scrape of his writing ware was the quiet flutter of a butterfly that had settled upon an adjacent pot of blue flowers, beaming in the moonlight. This man appeared to be in his late forties, the wrinkles across his face already revealed a tale of the slow stress he had shouldered in his pursuit for the medicine of all diseases; yet his character radiated a hint of passion. He had discovered something truly exceptional about the subject in front of him — something that would revolutionize the field of remedies.

The butterfly; violet, gleams from its perch on the sapphire petal, now shifting towards something much solid in formulation. It shows to be a sort of... mask? sculptured from a form of stone that relaxed braced beside a jar of blue broth. It couldn't have been Japanese, the design was too... un-natural. It occupied the display of a masculine face, its eyeholes sharp and moderately skewed in a point with its bulging lips practically paralleling a wicked smile. Two fangs slipped from beneath the top lip and resting against the underside, and a lengthy rim ran up the very top of the mask. It looked adjacent to an artifact that was some form of face-wear. But perhaps the exceptionally different fact about it was it seemed to have minor black blemishes across the exterior rows of its carving, a dehydrated form of liquid.

Behind the man is a figure, sitting in a chair with wooden wheels on each side; their face veiled by the obscurity of the barely luminous office, nevertheless their sickly form was obvious as day thanks to the exposed minimal muscle across their forearms, slipping from the edge of their garments. It's indeed troublesome to identify what gender they could be distinguished. lengthy hair, soft build... a woman perhaps? No.. the height difference just suggested overly uneven for it to be female. This was more along the boundaries of an extreme malnourished male; to the degree that their cartilages were pressed tight to the skin and that they lacked the physical strength to walk. Definitely an unfortunate circumstance, but one that had fallen to the recognition of this talented healer.

With the distinct clap of the book, the Doctor rose from his chair and gathered both the jar and face-mask; approaching his patient with an attracted view in their eyes. He was about to experience something no-one had ever known— and perhaps if this ran successfully, he could sway the very Emperor themselves. It was a modern miracle drug; a genuine 'Fountain of Youth' as the western world would put it, though in a much more cramped form than some fanciful pond.

"Thank you very much for agreeing to this, Kibutsuji-san. I know that it must have been hard to concede to such an experimental treatment, but I can assure you that I've had great results with my previous test subjects." The Doctor was making empty dialogue as he equipped the 'treatment', opening the jar of liquid to delicately lather the face-mask in it's greasy dew.

The man named Kibutsuji spoke soft and serenely, barely capable of lifting an arm from the disorder that coursed through his body. None of the soothsayers or specialists had been competent to resolve his condition, something he was born with and something he could particularly die of in the anticipated years. Every day he felt sluggish and insecure, he despised such a thing- seeking to be strong and remain on his own two feet, ultimately made to occupy a cursed existance in this frail body.

"Will.. will this work..? Will it fix me..?"

"Yes, Yes! It's an unorthidox method but it's absolutely astonishing. Please, sit still while I apply the apparatous. I assure you, the affects are quite effective!" The Doctor leans forth, folding the stone mask onto the slender man's features; the innard design of it was painted in the viscous blue coloration, frothing his face with a oduous stench. It's dew silthers from the pressure applied and beads down their collar, besmirching their garments in a darkened tinge that was icy to the touch. For a moment, Kibutsuji's frame tenses, a reasonable reaction of the cooling spill that had started to pool in his lap. He was confused- this felt unnatural and awfully inappropriate. Was this man just taking him for an ass? The further time passed, the more enraged he felt- he didn't appear any stronger, in fact he was starting to feel weaker!

"I-It's not working! Its not"

"N-Now please, calm down! I'm sure.. I'm sure it just takes a bit longer for the Human Physiology"

"H-Human?! You mean you haven't even tested this on-"

"Well, of course not- I've used mostly a form of primate and even a horse. the results were more than sufficent, let me check my notes, please just be patient-"

He couldn't remember what happened next, it's as if he blacked out from a spontaneous overdrive of emotions that dropped him forth in an uncontrollable fashion. Confusion, Anger, Embarrassment- they shower over Kibutsuji in an intensity of feelings. This was his last chance to feel normal, to be genuinely appreciated and not gazed at with sympathy for how he was. He wished to be strong, and more than anything, he wanted to remain on his own two feet. his body violently jolts, and with a totally bizarre sequence of events, he rose from his chair, lashing out at the Doctor in an irrational sense of bitterness. Within just a few minutes, they spluttered blood forth in a disgusting spray of gore, splattered out in a vast shower of crimson juice, smearing the face of the apparatus that had been practically fastened to his face, subsequently culminating in a rather unpleasant return.

Suddenly he lurched back, crashing to the floor in a hysterical shriek of shock as the mask he had strapped over his features extended several hair like spikes around their scalp. He could feel the rock jettisoning into his cranium and puncturing his head, a terrorizing experience resulting in a flailing body of the floor, clutching to the edges of their face constrictor in a neglecting attempt to wrench it from their face. They had just attained awareness merely to be propelled into a vulgar realm of excruciating agony, unable to do anything but squirm as his strength left him. The further he battled back, the further he could feel the biting tendrils penetrate deeper and deeper until they passed the very inner area of his greymatter, invading his head with both the painful pin-like vines of the mask, and the bluish liquid that had adhered to it in such vibrant stead. Something transpired that day, something both monstrous and horrific. Something that would sincerely danger the world while establishing one high above it to dominate.

It had to have been a good thirty minutes before a hand veered to that particularly same maple desk; this time more in mass and less boney than it had ever been. It's solely so that the moonlight dimly shined through the window in clear view to reveal the full form of the formerly dying male. No longer was he nothing but bones, but; he settled at least a generous foot taller with the very clothing he carried splitting at the seams from his unique augmented size. Muscles bulge from his arms and legs, subsequently capable of upholding him with no aid. He felt stronger... stronger than forever before. There was something peculiar still; something that felt... off. The sight of the deceased man at his feet should have troubled him, but the longer he gazed at his lost practitioner, the further his mind turned to need. This awareness, this strive that he had never known before — it was starvation. A vice-like hunger that had devoured his senses. Like a ferocious beast, he plunges to the ground and starts to violently separate the corpse apart with little to no effort, exceptionally stronger than an average man, and faster too. The gut wrenching sounds of meat tearing and blood sloshing saturated the room in gorish echo. The more he devoured, the stronger he felt — it was euphoric.. it felt right. It felt.. wonderful.

Hello everyone! This is a project I've been considering for a long while, and something I've wanted to write for an even LONGER time. The idea of Demon Slayer taking place between Part 1 and 2 has always intrigued me, especially when you look at how close the similarities are! So, I've decided that I was going to finally write a fic, but instead of throwing in Jonathan or Joseph. I figured I'd take another route and throw Josuke in instead! Right now I'm looking for feedback and constructive criticism, to see if I actually move to making more chapters, But please let me know what you guys think!