Hashira

The Pillars are the top-ranked and most powerful swordsmen among the Demon Hunters in the Demon Killing Corps who serve as its elite warriors.

Overview
The Pillars are the nine most powerful swordsmen among the Demon Hunters who sustain the Demon Killing Corps. Those who are of lower rank may be killed at a freighting rate, as each Pillar possesses a distinct breath style which is learned from a cultivator or developed through extreme training. The group is overseen by the leader of Demon Killing Corps Kagaya Ubuyashiki.

Pillars are constantly searching for a Tsuguko (Successor), that can take their place when they die or retire. Each Pillar is assigned to a specific region that they need to protect. They also need to gather information about demons and improve their own swordsmanship, because of their busy schedule, they usually would only train their Tsuguko. To become a Tsuguko, you either apply and a Pillar accepts or you get scouted by him. Being of the same Breath Style helps, but a Pillar still can take a successor with different Breath Style.

The time needed to become a Pillar though hard training is usually 5 years for normal people, but talented and fast learners can do it in 2 years. To become a Pillar, you will also need to defeat one of the Twelve Demon Moons or 50 demons. Swordsmen who can use the breaths of flames and water have become Pillars in every era, no exceptions.

History
After the fight with Lower Moon One, Enmu, the Upper Moon Three, Akaza, showed up. A fight between Akaza and Kyoujurou Rengoku occurred. As a result of the fight, Akaza fled, but Kyoujurou died from his wounds and left a vacant Pillar spot.

Not long after that, Tengen Uzui took Tanjirou Kamado and his group to a mission in the Red Light District. There, they encountered Upper Moon Six, Gyuutarou & Daki. As a result of their fight, Gyuutarou and Daki died, and Uzui lost his left eye and left arm, forcing him to retire and leave a second vacant Pillar spot. But despite forced retirement Tengen (along with his wives) assist with Demon Hunter Training Program.

After Kibutsuji Muzan broke into the Ubuyashiki Manor, he was attacked by Himejima Gyoumei the Rock Pillar in an attempt to slay him, but Muzan escaped into the Infinity Fortress with a number of demon slayers chasing after them only to be separated by Nakime, the current Upper Moon Four.

A number of duels broke out in the Infinity Fortress between demons and slayers: the pillars and the other demon slayers faced off against numerous demons who all had equivalent strength to a Lower Moon, Kochou Shinobu attempted to kill the Upper Moon Two, Douma, who was responsible for the death of her sister, but she was killed and was absorbed by Douma, who is currently engaged in a battle with her apprentice, Kanao Tsuyuri. Agatsuma Zenitsu ran into the new Upper Moon Six, is former apprentice brother Kaigaku, and engaged him in a duel to the death in which Kaigaku had an overwhelming advantage and nearly killed Zenitsu, but Zenitsu managed to insta-kill Kaigaku with a secret technique he created. Elsewhere, Tanjirou and Tomioka Giyuu were ambushed by the Upper Moon Three, Akaza.