Demon Slayer Core

The **Demon Slayer Core** is a massive organization that has existed since ancient times, dedicating its existence to protecting humanity from demons. Throughout time, it grew and developed, branching into the version that is currently seen in the story.

## **Overview**

The Demon Slayer Core is an organization dedicated to hunting and killing demons. Most members of the Demon Slayer Core are combatants, known as Demon Slayers. That said, one can still be a member of the Core while not being a fighter. Medics, while usually slayers in their own right, can be entirely unarmed civilians that simply volunteered or applied to work on the Core Hospital. Others may work more menial labor, such as janitors, cooks, dressmakers, washers and even engineers. Additionally, all the people born in the Blacksmith Village are registered members of the Core, but are not required to partake in any labor.

Originally, the Demon Slayer Core was not only unrecognized by the government, but it also used to be directly opposed by such, with the Slayers not being allowed to carry their swords in public. However, after the Core Reformation, which led to a much better structured system and organization, the Core has since been recognized, and while not endorsed, nor absorbed by the government, Slayers receive tax cuts and are not obligated to join in the war effort.

While originally entirely dependant on the Ubuyashiki Family for funding, the Core has since branched out into more ways of gaining money. From sponsors that arised as the Core's existence became an open secret, to more nieche commercial interests by the Core's own members, the organization now has many ways of earning enough money to sustain itself.

## **History**

The Demon Slayer Core was founded approximately a thousand years ago during the Heian Era. This occurred after Muzan Kibutsuji, a distant relative of the current Ubuyashiki family, inadvertently became the very first demon. As a result, a curse befell the Ubuyashiki bloodline, causing subsequent generations to suffer from premature deaths. They took on the responsibility of leading the battle against Muzan and his demons, believing that by eradicating demons from the world, they could break the curse that plagued their bloodline.

In the centuries that followed the establishment of the Core, they achieved barely any success in eliminating the demons Muzan created, much less was anyone able to reach the Demon King himself. However, during the Sengoku era, the tides turned. A talented swordsman named Yoriichi Tsugikuni joined the Core after his wife was slain by a demon. He imparted his knowledge of Total Concentration Breathing onto the Hashira of the Demon Slayer Core. He also endeavored to teach them a Breathing Style known as Sun Breathing, but despite their efforts, none of them could match Yoriichi's level of mastery, so he modified the techniques to suit their individual strengths. These modifications formed the foundation of the first Breathing Styles, from which numerous other styles emerged as branches. The swordsmen of that era were already highly skilled, and when combined with the Breathing Styles, their power increased exponentially. Furthermore, distinct Marks began to appear on the bodies of these swordsmen, further enhancing their abilities. This era of Demon Slayers came to be known as the Golden Age, as they displayed incredible prowess in vanquishing demons with astonishing force and almost eradicated all demons.

However, the Marked Demon Slayers paid a high price for their power, as their lives became forfeit. Despite their perfected techniques, they had no successors to carry on their legacy. Faced with the belief that there was no future for him, Yoriichi's twin brother, Michikatsu, was approached by Muzan, who sought to transform a swordsman skilled in Breathing Styles into a demon. Michikatsu accepted Muzan's offer, renamed himself to Kokushibo, and proceeded to kill the then-Oyakata-sama, presenting the leader's head to Muzan as a display of loyalty. Shortly after, Yoriichi encountered Muzan and nearly succeeded in killing him, but the Demon Progenitor managed to escape. Yoriichi shouldered the responsibility for his brother's betrayal and his own failure to eliminate Muzan, leading to his expulsion from the Demon Slayer Core.

After his near-death experience, Muzan went into hiding for nearly a century, patiently waiting for his nemesis to pass away of old age. With Yoriichi out of the picture, Muzan set his sights on destroying the Demon Slayer Core and eliminating the Ubuyashiki Family, the source of the Core's support. To achieve his goal, Muzan formed an organization called the Twelve Kizuki, comprised of the twelve strongest demons, including Kokushibo, with the sole purpose of exterminating every last Demon Slayer. Over the centuries, the Core faced numerous life-threatening situations and came perilously close to annihilation, as no Demon Slayers were able to match the power and skill of their exceptional predecessors from the Golden Age and were mercilessly killed by the demons.

Ultimately, during the Taisho era, a new generation of Demon Slayers emerged that was regarded as the strongest since the Golden Age. Among them, Tanjiro Kamado, a practitioner of Sun Breathing, is the first Demon Slayer to awaken the Mark, after which some Hashira followed suit. The momentum generated by Tanjiro's awakened Mark and the Pillars carrying enough strength to rival the Golden Age Pillar lineup culminated into a battle of massive proportions in the extradimensional Infinity Castle. The battle ended on a stalemate, with Muzan Kibutsuji retreating and going on a near total reclusion of demonkind for twenty five years, where the amount of cases diminished significantly.

During these twenty five years, the Core went through significant changes. Seeing the positive result of the Pillar Training regiment applied to the Slayers shortly before the Battle, the Pillars eventually came up with a system that allowed for continuous high-level training, all the while putting the entire organization into a much further coalesced operation, rather than the fairly open and poorly-managed original Core. The Core Reformation, as it was later dubbed, added systems that now every Slayer considers to be nearly intrinsic to the organization. From the Pavilions and Sects, which were built as ways for Slayers to train with individuals of their particular Style in a much more concise manner, with competent teachers and a fairly levelled education, to the Cultivator Trial, which is designed as a way to assign each individual trainee to their best suited Breathing Style, avoiding the incompetence of the previous Core, where many Slayers used Styles incompatible to their bodies simply because of the luck factor of which master they ran into.

## **Positions:**

### **Oyakata-Sama:**

The leader of the Demon Slayer Core, revered as **Oyakata-sama** by his subordinates, serves as the head of the organization and is traditionally a member of the Ubuyashiki family. He undertook crucial responsibilities such as coordinating the deployment of Demon Slayers to areas plagued by demon activity, overseeing the Final Selection for aspiring Demon Slayers, and conducting meetings with the Hashira. Originally, the Oyakata-Sama possessed intense power over the Core, but their overall power was diminished after the Core Reformation, where they tend to act more into roles of judgement and guidance.

### **Pillars:**

Second only to the Oyakata-Sama and sharing equal say to one another, Pillars are the backbone of the Demon Slayer Core, tending to be the ones to lead advances against powerful opponents and managing nearly all Slayers under their particular Sect or Pavilion. Pillars used to be mainly trusted handymen for the Oyakata-Sama originally, while in the current state of the Core they make most decisions with weight to the organization.

Pillars can hand out a paper-thin sheet of nichirin metal engraved with their given title as a means to officialize an order to someone such as a Kakushi, who otherwise would have no authority.

### **Tsuguko:**

The ones directly under the Pillars, Tsuguko are their apprentices and second-in-commands, being expected to lead their respective Sect in the Pillar's absence, and be ready to take it over should the worst happen. Tsuguko are much more poignant and respected after the Core Reformation, as before they had effectively no distinction from the average Slayer, other than a rank that only affected them should their master pass away.

### **Cultivators:**

While lacking agency in more hands-on operations, Cultivators are not only required for a Sect to properly run, but also many of them usually mean a Sect flourishes. An abundance in trained teachers of a particular Style, which can teach their techniques, if not create new ones, is vital for the Core's operation, and their duty cannot be overstated.

### **Squad Leaders:**

Local officers in the Core, the Squad Leaders are the lowest form of direct authority that the average Slayer may find. Usually, this role is reserved for those that are too old, or not talented enough to become Tsuguko, but aren't experienced enough to become Cultivators. That said, they are expected to be good leaders, and that is a requirement for their promotion.

### **Unranked Slayers:**

The main bulk of the Core. Whether belonging to a Squad, or acting independently, they represent the majority of the members, and are the heart and soul of the organization. There are hundreds of skilled and dedicated individuals who have taken up the noble duty of hunting down and eliminating demons.

### **Kakushi:**

The all-purpose members of the Core, whose work is to work hard. Kakushi are transport, medical help, and espionage rolled into a single duty. Every Kakushi member is expected to be well-versed in all those areas, and are expected to even die for their Slayer companions. Kakushi are able to elect a leader between themselves to manage their positions, pay, and average workload, even if said leader has very little wiggle room.

### **Service:**

Service members differ from Kakushi as they are not intended to, nor supposed to be in the front lines. They are divided into a handful of jobs, from cooking, cleaning, washing, sewing, all those services, some of which were taken off of the Kakushi in order to add a more field presence to their role.

### **Swordsmiths:**

The Swordsmiths are a part of the Demon Slayer Core that is nearly entirely disconnected from everything else. Not only is their leader simultaneously their representative, but also the Blacksmith Village's actual political leader. The Swordsmiths are not expected to become Slayers, nor to do any other job than to merely craft the weapons that Slayers will use.

## **Funding:**

Originally entirely funded by the Ubuyashiki Family, the Demon Slayer Core has since branched out into many other ways of gaining money. Both from investors from outside due to the open secret of their existence, but also from their own market. Slayers are, while training, also used to gain money in other, less conventional ways. Notably:

* Members of the Leaf and Flower Sects are known to sell potted decorative plants, if not seeds for farmers. In both cases, they tend to be species bred and created in the Core, meaning they are exclusivities of the Sects. A notable export is the yellow colored wisteria, which was originally bred for decorative purposes, is now sold worldwide as decoration.
* Members of the Beast Sect, while going for hunts, occasionally sell the meat and hide of the animals they end up killing.
* Members of the Stone Sect are known to sell statues and other hand-made sculptures made both of raw stone and clay.
* Members of all Sects occasionally act as builders for certain structures: Coolers (Snow), Hot Springs (Steam), Pools (Water), Gardens (Flower and Leaf), Animal Pens (Beast).

## **Locations:**

The Core is generally situated in many different areas, with six main hubs, and a few external buildings. The six hubs, which are known as the Core Central, the Water Pavilion, the Flame Pavilion, the Stone Pavilion, the Thunder Pavilion, and the Wind Pavilion, are stone fortresses with incredibly tall walls that act as true strongholds. The location of the Core Central is a secret, while the other Pavilions are public. This is due to a lack of actual fear in their invasion, since the magnitude of an attack would need to be immense to actually destroy any of them.

### **Core Central:**

The Core Central is a massive fortress in an undisclosed location only known to the Pillars and the Tsuguko, as to any other Slayer, regardless of rank, may only be brought to it via kakushi transportion in a way very similar to the Blacksmith Village's own way of remaining hidden. The Core Central features the Core Hospital, which is the main hub for medicinal knowledge and action in the entire organization. Outside other utility buildings, the Central Tower is where Pillar Meetings and Trials are situated, in the very top and bottom of the tower respectively.

### **Pavilions:**

All Pavilions, from the outside, are built with dark gray, thick stone walls, with guard posts all above the walls, which are entirely solid. The guards, from above, warn of visitors. Each Pavilion only has a single wooden doorway, which is large, and only opens from the inside, by a mechanism, rather than actual force.

Each Pavilion can house five entire Sects. One centermost, at the very end of the Pavilion, which is also its denominator, and it is the largest of all Sects, and four around the main Sect. If there are too many viable Sects, the Pavilion is to be expanded. Sects are divided from one another by stone walls of the same material as the outer walls. They are shorter and thinner, however, and they do have more accessible gates. The only exception to this is the Beast Sect, whose walls are entirely closed, and the only entrance is the gate at the Tower

* **Water Pavilion:** The Water Pavilion, on its main center, features deep lakes decorated by lily pads and other aquatic plants, while also featuring small fish such as koi, that either the slayers, or the staff feed regularly. Its wisteria trees are blue, complimenting the generally cold colored aesthetic of the place

* **Flame Pavilion:** The Flame Pavilion, while lacking distinctive features when it comes to plantlife, having pretty much only the especially bred red wisteria trees, their story and purpose elaborated upon in the Thunder Pavilion section, it does have braziers and torches scattered all throughout the place, completely ditching electrical, or less abrasive lighting.

* **Stone Pavilion:** The Stone Pavilion, on its main center, is generally normal in appearance, with regular gardens that have no prominent amount of greenery, and its wisteria trees are colored white.

* **Thunder Pavilion:** The Thunder Pavilion is dotted by mostly orange and yellow plants and flowers, making it appear as if it is constantly within an autumnal season. The Yellow Wisteria trees are a variant specifically bred to maintain its shedding colors. Since they were created by Core Affiliated Gardeners (Mostly Leaf Sect Slayers), the commerce of their saplings is yet another way that the Core earns money.

* **Wind Pavilion:** The Wind Pavilion, on its main center, has a lot of greenery and gardens, and is mostly decorated by deep purple wisteria trees. It is divided into four Sects.

### **Swordsmith Village:**

The Swordsmith Village is the dwelling place of the skilled swordsmiths who craft powerful weapons for the Demon Slayers in foundries and workshops. To safeguard the village from potential demon threats, its precise whereabouts are closely guarded and kept confidential. The location of the Village, since the original attack by Hantengu and Gyokko, has shifted to another, yet still new location

### **Nichirin Mines:**

Located near the original Swordsmith Village, the location remains a secret to most Slayers, and only due to its comparative lack of importance is it even allowed to publicly exist. A demon attack here would barely bring any devastation, so the Core did not care to hide it as well as it does with the Swordsmith Village. Aside from that, the mines and the nearby town being inconspicuous in appearance, rendering them unremarkable.

### **Fujikasane Mountain:**

Mount Fujikasane, a mountain enveloped in a blanket of Wisteria and invested with demons at the area around the mountain top, serves as the venue for the Final Selection. This entrance exam, organized by the Core, challenges aspiring candidates who seek to join the ranks of the Demon Slayers.

### **Butterfly Mansion:**

The Butterfly Mansion was an establishment connected to the Corps and functions as a dedicated recovery base for injured Demon Slayers. In the mansion, injured individuals received essential medical care for their injuries and undergo rehabilitation training to regain their strength and skills. After the Core Reformation rendered it redundant, the Butterfly Mansion returned to being the residence of the Kocho Family and its aggregates.

### **The Shelter:**

The Demon Slayer Core, more often than not, is confronted with children left orphaned by a demon attack, and with nowhere else to go, they are taken to The Shelter, a place where they may grow up, and gain basic education, until they are old enough to set off on their own, or join the Core directly. One person that has lived in The Shelter before becoming a Slayer is Kaguya Yamabiko.

## **Known Members:**

### **Active:**

#### **Tsuguko:**

*\*Despite being technically the Tsuguko of the Steam Pillar, Aya is not listed as the Steam Tsuguko due to the mismatched Breathing Styles*

### **Inactive:**

#### **Unranked:**

(Mist)

## **Trivia:**

* The Demon Slayer Core does not keep the Marks a secret like before, but the instructions on how to obtain them are.
* The Demon Slayer Core was requested to have the Slayers participate in WW2, and the nichirin metal to be used for weaponry by the government. Both were vehemently refused.