Koichi Ubuyashiki

**Koichi Ubuyashiki** (産屋敷 子一 *Ubuyashiki Koichi*) is one of the two sons and eldest child of Kagaya Ubuyashiki. After his father's passing, he leads the Demon Slayer Corps as the 98th and final leader.

## Appearance

Koichi has light, pale skin and possesses a small, weak-looking physique similar to his siblings. Due to his different attitude to his younger brother Kiriya, he was not raised as a girl and therefore has a more natural, messy hairstyle with white hair that fades to a light purple.

In his first appearance with his father, he is seen wearing a pale white robe with dark purple hakama trousers and a wisteria headpiece. During his full appearance at the Hashira Meeting, he wears a purple kimono with patterned flowers and a green obi. For the remainder of the series, he does not wear a wisteria headpiece.

Later on, after he becomes the leader of the Demon Slayer Corps, he wears a black kimono with a long white haori that's reminiscent of his father.

His eyes are usually covered by a dark shadow, and he is mostly seen holding a traditional wooden fan which obscures the lower half of his face.

## Personality

During his first appearance at the Hashira Meeting, Koichi is seen as a quiet, mysterious and intelligent individual. He greets the Hashira before his father arrives, and congratulates them on their recent successes. Since his position as a child of the Ubuyashiki family meant he had no knowledge of the Hashira's duties, it amazed them that he was able to deduce their successes so quickly. Additionally, when he noticed Tanjiro Kamado was also present at the meeting, he greeted him with vague blessings and prayed for his future health.

Later, upon his father, mother and sisters' deaths, Koichi is seen to be incredibly skilled at leading, strategic, and calm when he became the new leader of the Demon Slayer Corps. He organizes his remaining siblings and remains unfazed by recent happenings, despite losing half of his family and having no time to mourn them. He shows more emotional strength than his younger siblings, who momentarily broke into tears in grief.

Although his plan led to the slaughter of many Demon Slayers, he is not seen to break under stress albeit it is clear he feels guilty for their deaths and prays for their souls to return to the heavens to rest.

He remains serious and mature throughout the final battle, keeping his siblings involved and proving that despite his distant personality, he cared about his siblings and consoled them when they were struggling in their moments of leadership.

After the final battle ceases, Koichi is seen to immediately rush to the battlefield and help clear the area, even giving injured Slayers medical attention and praying for those that had died. Before the disband of the Demon Slayer Corps, he visits the graveyard where all fallen Demon Slayers were buried, and did the same for those that died in the final battle before walking through it with his younger brother Kiriya and naming all of them.

## History

Koichi was born to Kagaya Ubuyashiki and Amane Ubuyashiki as their first child and first of two sons. He was born four years before his younger siblings. As the eldest son of the family, he becomes the male heir, the next head of the Ubuyashiki family and the first in line to inherit his father's position as commander of the Demon Slayer Corps.

At first Koichi was believed to be weak and frail due to his small figure, but he showed proficiency in wielding different types of shuriken and expressed his potential hope to become a Demon Slayer himself.

After his siblings were born, he showed great care and love towards them, often looking after them when his parents were unable to and occasionally, after growing older, taking over for his father during Hashira Meetings when the latter was unable to attend.

## Synopsis

### Final Selection Arc

Koichi asks his father how many had survived the year's Final Selection, and states that the five who had passed seem to have potential. He deduces that they are all of different fighting techniques, correctly suspecting that one does not utilize a Breathing Style.

### Rehabilitation Training Arc

Koichi is present at the Hashira Meeting and states that he pities Tanjiro greatly, before congratulating the Hashira on their recent successes. He watches his father address the Hashira, and threatens Sanemi with possible demotion if he dares to harm Nezuko who was still vulnerable at the time. Once Sanemi retreats, he offers to help Tanjiro back to the Butterfly Mansion, carrying Nezuko's box on his shoulders. He reaches the Butterfly Mansion and leaves Nezuko with Tanjiro, thanking the latter for bravely fighting Rui at Mount Natagumo and bowing in respect.

### Hashira Training Arc

After the events of the Swordsmith Village Arc and Mitsuri and Muichiro's recovery, Koichi holds an emergency Hashira Meeting. He apologizes that neither his father or his mother could be present, before explaining that the Corps are in a dire situation. He introduces the idea of Hashira Training, which is then agreed upon between each of the Hashira.

### Infinity Castle Arc

After witnessing his father's, mother's, and eldest sisters' deaths, Koichi immediately takes the place of his father and instructs his remaining siblings to gather whatever they could on the Infinity Castle once the Demon Slayers reach it. He receives Yushiro's talisman and watches through the crows, with him and his siblings working together to map out the dimension. He instructs the Hashira and the other Demon Slayers to work together, however they are all split up and his plan is foiled.

After hundreds of Demon Slayers are slaughtered, Koichi prays for all of them before attempting a different plan which manages to work out. He is relieved that his plan has worked, and all of his siblings see their father within him. Koichi instructs his siblings to not lose focus and tell them that they will have time to grieve once Muzan is defeated.

### Sunrise Countdown Arc

Koichi begins to break under the pressure of leading the Corps after witnessing the deaths of six of the eight remaining Hashira, and yells for Giyu and Sanemi to not give up fighting, knowing the battle wasn't over even though Muzan was defeated. When Tanjiro Kamado is turned into a demon, Koichi runs towards the battlefield and reaches it to see Nezuko Kamado fighting her brother while he attacks those surrounding him. Koichi realizes that he would have done the same for his siblings, before catching a vial of the antidote from Kanao Tsuyuri and throwing it at Tanjiro with two shuriken surrounding it. When the vial hits the latter, he stops attacking people and falls unconscious, resulting in Koichi instructing the survivors to tend to their own wounds and making sure the two siblings were still alive.

After the battle ends, Koichi holds a final Hashira Meeting with the surviving two Hashira, thanking them deeply for their service to the Demon Slayer Corps. He then gathers all the surviving Demon Slayers and thanks them on the behalf of the Ubuyashiki Family, before disbanding the Corps for good. He rebuilds the Ubuyashiki Mansion with his siblings in honor of his father, mother and sisters' sacrifices.

### Legacy

Over a century after Muzan's defeat, Koichi is still alive and the oldest living person in Japan alongside his younger siblings. He was interviewed by many reporters, but responded vaguely; he didn't know what was going on due to his elderly age. The fact that he and his siblings lived so long is proof that the illness which previously cursed their family is now gone along with Muzan.

## Abilities

**Shuriken Proficiency:** Throughout his childhood, Koichi practiced throwing shuriken as a fighting style and hoped he would become a Demon Slayer. Despite his position as a member of the Ubuyashiki family prevented him from doing so, he continued to practice with his shuriken and became extremely proficient in fighting with them. He was able to throw and direct a vial of the antidote towards Tanjiro Kamado while the latter was fighting against his sister, being extremely accurate and hitting him correctly. This makes Koichi differ from his siblings since he had skills in fighting and was slightly more physically strong than the others.

**Extraordinary Memory:** Koichi has shown extremely good memory. He and his siblings are able to map out and memorize the nearly constantly changing Infinity Castle, creating accurate maps to navigate and guide the Hashira through it in real-time.

**Foresight:** Similar to his father and his ancestors, Koichi has a high, almost prophetic intuition, being able to make accurate guesses and hypotheses that were often proven right through intuition alone. He managed to correctly deduce that Genya Shinazugawa didn't use a Breathing Style after only hearing his name once while talking to his father about the year's Final Selection survivors.

**Leadership Skills:** Much like his father, Koichi displays advanced skills in leading and commanding an army into battle despite his young age. He is able to immediately take command of the Demon Slayer Corps' command structure and assist the Hashira as logistical support, guiding them into battle.

**Longevity:** Due to their relative, Muzan, becoming the first demon, men within the Ubuyashiki family were cursed with a mysterious illness, causing them to usually die in their thirties. However, after Muzan's death, the curse was seemingly lifted. In fact, Koichi and the rest of his siblings were blessed with extremely long lives, still being alive over a hundred years later with Koichi being the oldest living person in Japan.

## Equipment

**Dual Bo-shuriken:** Koichi requested for two Bo-shuriken to be forged for him at a young age. His Bo-shuriken had four points and were tipped with sharp silver, which seemed to always be shiny no matter what they hit. He used these to secure the vial of the antidote when attacking Tanjiro Kamado, and these were later kept in a museum alongside Kyojuro Rengoku's handguard and Tanjiro Kamado's hanafuda earrings.