In short
The Ubuyashiki family has led and funded the Demon Slayer Corps for a thousand years in Demon Slayer. It is paying for an ancestor’s fault: Muzan Kibutsuji belonged to this line before his transformation, and since then every son of the family is born with an illness that kills him before thirty. A priest gave them two instructions, and the second was to kill the first demon.
Contents
Behind the nine Hashira and the hundreds of fighters in Demon Slayer, there is a family of civilians who carry no weapons, die young generation after generation, and have paid for everything for a thousand years.
This article goes back over the Ubuyashiki story: the origin of the curse, the priest’s instructions, the founding of the Corps, each member’s role, and what becomes of the family after the war. Our page on the directory of the series’ characters places it in the whole.
Who are the Ubuyashiki?
| Member | Role |
|---|---|
| Kagaya Ubuyashiki | head of the Corps during the story, twenty-three |
| Amane Ubuyashiki | his wife, his relay and voice at meetings |
| Kiriya Ubuyashiki | the son, successor at eight, raised as a girl |
| Kanata Ubuyashiki | his sister, coordination and liaison |
| Kuina Ubuyashiki | his sister, coordination and liaison |
| Hinaki Ubuyashiki | his sister, died with her mother |
| Nichika Ubuyashiki | his sister, died with her mother |
| Link with Muzan | a common ancestor, a thousand years earlier |
| The family’s role | founding, funding and leading the Corps |
| The leader’s title | Oyakata-sama, the master of the house |
The family holds a special place in Demon Slayer. It does not fight, carries no sword, and has no power, yet nothing the demon slayers do would exist without it.
Its authority rests on tradition and money. The Ubuyashiki pay for everything: the uniforms, the swords, the crows, the care and the logistics of an organisation the state does not recognise.
Their house is the best-hidden place in the story. Nobody outside the inner circle knows its address, and the family has never had a bodyguard in a thousand years.
Their fortune has an origin the story mentions in passing. The family has a gift of foresight that allows it to anticipate certain events, and that is how it amassed enough to fund an organisation for a thousand years.
The rest comes down to discretion. Demon slayers appear in no register, receive no public pay, and depend entirely on this private purse.
They pay for everything
The Ubuyashiki fund the swords, the uniforms, the care and the crows. The Demon Slayer Corps has no other resource.
The character the family puts on the back of every uniform appears on one of the shop’s caps.
Corps cap
The kanji 滅 brushed in white on the front panel, cotton with a vintage finish, seven colours.
View the product · €29.90The original fault
It all goes back to the Heian era, a thousand years before the Demon Slayer story. A member of the family, in fragile health, receives an experimental treatment meant to save him.
The treatment produces something else. The man becomes the first demon in history, takes the name Muzan Kibutsuji, and begins a career that is still going at the time of Demon Slayer.
The family pays immediately. A curse strikes the line, and every boy is now born with an illness that kills him before adulthood.
The mechanism is never explained other than by this blood tie. The series treats it as a debt: the line produced the evil, the line bears its mark.
Our article on Muzan Kibutsuji, the first demon tells of this transformation from the side of the one responsible.
The detail makes the situation more bitter still. The man treated at the time was a young man of fragile constitution, doomed before twenty, exactly like those the curse strikes today, and the treatment was trying to save him.
A treatment gone wrong
A sick Ubuyashiki receives an experimental treatment in the Heian era. He comes out of it as the first demon in history.
The priest’s two instructions
In Demon Slayer, the family consults a priest to try to lift the curse, and receives two precise instructions.
The first concerns marriages. Male heirs must marry a woman chosen by a priest, which the line has applied to the letter ever since.
The result is measurable. The sons stop dying as children and reach adulthood, even if they remain ill and die before thirty.
The second instruction is a life programme. The Ubuyashiki must make it their goal to eliminate the first demon, for the curse will last as long as the taint remains in the line.
From this instruction the Demon Slayer Corps is born, as our article on the Demon Slayer Corps and its history details.
The instruction on marriages has an unexpected consequence for the story. Ubuyashiki wives enter the family knowing what they are committing to, and all of them take on this role without the series showing a single hesitation.
Two orders, a thousand years of obedience
Marry a woman chosen by a priest, and kill Muzan. The family has applied these two instructions since the Heian era.
A thousand years of dying young
The curse always follows the same course in Demon Slayer. The skin deteriorates starting from the face, the body weakens, the defences give way, and death comes between twenty and thirty.
The leader in the story is the example. Kagaya Ubuyashiki loses his sight, then the use of his legs, then the ability to leave his bed, within a few months.
So succession is organised very early. Each generation trains the next from childhood, because nobody knows how long the leader in office will last.
Kagaya’s case shows it well. He takes on the role at four, after his father’s suicide, and our article on Kagaya Ubuyashiki, the demon slayers’ leader tells of his path.
So the family lives in permanent mourning. Every male child knows, as soon as he understands, that he will not reach thirty.
Never past thirty
No man of the family reaches thirty. Succession is prepared from childhood, in every generation.
Amane, the wife
In Demon Slayer, the wife’s role is anything but decorative. Amane Ubuyashiki, from a family of priests and married to Kagaya when he was thirteen, speaks in his place when his voice fails, and ends up presiding alone over an emergency meeting of the Hashira.
She also runs the house and the children. Five children, a dying husband, and the secret of an entire organisation rest on her during the last years.
Her attitude mirrors her husband’s. The same calm, the same courtesy, the same refusal to show what the situation costs her, even in front of angry fighters.
She dies in the house’s explosion, with two of her daughters. Our article on the Infinity Castle and how it works tells what immediately follows that night.
The choice is deliberate on their part. The family knew what was going to happen, and nobody left the house.
She knew, and she stayed
Amane and two of her daughters die in the explosion Kagaya prepared. None of them left the house beforehand.
The five children
Demon Slayer’s siblings are five quintuplets, a boy and four girls. All of them work for the Corps long before they are old enough to understand what it does.
Kiriya is the son and therefore the successor. Raised as a girl, it is in a purple kimono that he welcomes, with his sister Kanata, the Final Selection candidates.
Kanata and Kuina handle liaison. The two girls coordinate the information arriving from the field and the orders going back out, which becomes decisive during the final battle.
Hinaki and Nichika die with their mother in the explosion. The two girls appear in only a few scenes, always beside their father.
The story does not dwell on their age. The three survivors are children, and they lead a Corps of several hundred fighters during the deadliest night in Demon Slayer.
Their composure is striking from the Final Selection. When Genya Shinazugawa manhandles Kanata, Kiriya remains impassive.
Children in command
Three children survive the explosion and take over coordinating the Corps. They are eight years old.
The eight-year-old son who takes over
The handover happens in one Demon Slayer night, without ceremony. Kiriya Ubuyashiki becomes head of the Demon Slayer Corps the moment his father’s house blows up.
He takes on the role immediately. The child gives orders to adult fighters, announces the losses, reassigns positions, and serves as everyone’s fixed point.
His two sisters handle logistics with him. The three follow the course of the clash thanks to the talismans of an allied demon, attached to the messenger crows.
Our article on Yushiro, Tamayo’s assistant details this arrangement, and our article on the Corps’ Kasugai crows explains the network used.
The detail to remember is the age. The Demon Slayer Corps wins its thousand-year war under the orders of an eight-year-old child.
Eight years old and in charge of everything
Kiriya Ubuyashiki takes command of the Corps on the night of his father’s death. He is eight, and he holds on until morning.
You will find the crows that link Kiriya to the fighters right down to the shop’s watches.
Crow watch with gold dial
Gold dial with Roman numerals cut in a fan shape, black case, acrylic feather with a crow silhouette.
View the product · €69.90How does the family protect its secret?
The house’s location is the best-kept secret in Demon Slayer. No demon must be able to find it, and the whole organisation is built around this constraint.
The reason is historical. In the Sengoku era, a demon slayer who went over to the demons’ side killed the leader of the time and brought his head to the first demon. His six-year-old son succeeded him on the spot.
The measures taken after this tragedy still hold. Visitors are led there blindfolded, and a specialised brigade takes care of anything that might leave a trace.
This brigade is detailed in our article on the Kakushi, the brigade in the shadows, and our article on Kokushibo, Upper Moon One tells of the original betrayal.
The arrangement then holds for nearly four centuries. It gives way at the end, because the leader in office decides himself to open the door.
Even the Hashira only go there when summoned. The house’s garden serves as a meeting room, the fighters kneel there in a semicircle, and nobody stays on once the session is over.
An address nobody knows
Nobody knows the address of the Ubuyashiki house. The secret holds for four centuries after the betrayal, and gives way deliberately.
Why does Muzan come in person?
Demon Slayer’s first demon goes himself to kill Kagaya, which he almost never does. The reason lies in what this family represents for him.
The Ubuyashiki are the only humans he considers a personal problem. A thousand years of pursuit, generations of leaders, and an organisation that has never stopped looking for him.
The encounter turns to the dying man’s advantage. Kagaya talks, smiles, speaks of the family and the shared blood, and blows up the house at the moment of his choosing.
The first demon then discovers he has been outmanoeuvred by a man who could no longer get up. Our article on the last fight against Muzan tells what follows that night.
The episode gives the family its only direct victory in a thousand years. No Ubuyashiki had ever touched the first demon.
The only direct victory
No Ubuyashiki had ever wounded Muzan in a thousand years. Kagaya manages it without getting out of bed.
The ancestor turned demon has his Muzan Kibutsuji collection, right down to the shop’s necklaces.
Muzan steel tag necklace
Steel military tag: Muzan under the brim of his pale hat, white collar buttoned high, red eyes.
View the product · €17.90What becomes of the family
At the end of Demon Slayer, the curse dies out with its origin. The demons of his line disappear on the death of the first of them, and the debt that weighed on the line disappears with them.
The epilogue confirms it with an image. The son, now a centenarian, has become the oldest man in present-day Japan, which had happened to no man of the family in a thousand years.
So the priest consulted in the Heian era was right. The condition for the cure was Muzan’s death, and the family took a thousand years to obtain it.
At the same time the house loses its reason to exist. The Corps is disbanded, the fighters go home, and the Ubuyashiki stop funding a war that no longer exists.
Our page on all the series’ arcs places this ending, and our article on what becomes of Tanjiro at the end tells of the aftermath for the fighters.
The first to grow old
Kagaya’s son appears very old in the epilogue. No man of the family had passed thirty in a thousand years.
What the family brings to the story
The Ubuyashiki solve a problem many stories leave aside. A clandestine organisation of several hundred people requires funding, logistics and leadership, and Demon Slayer takes the time to show them.
The family also serves as a mirror to the opposing camp. Two organisations, two leaders of the same blood, and two opposite ways of treating those who obey.
Finally, it gives the story its dimension of family debt. The demon slayers fight not only for the victims, but for a fault committed a thousand years earlier by a sick ancestor.
Our page on the series’ demons and their hierarchy presents the other organisation.
Two organisations, one blood
The Demon Slayer Corps and the demons are led by two descendants of the same family. Everything separates them in how they command.
