Yoriichi and Michikatsu

Yoriichi was a calm and respectful individual who wore a solemn and reserved expression at all times, rarely showing outbreaks of emotion. Generally, Yoriichi had a matching low and serene disposition, evident when he killed demons without changing expression or when Muzan was caught offguard by his immense skill because he appeared unassuming. Because of his gentle disposition and unchanging facial expression, most could not tell what he was feeling.

He was also extremely humble, seeing himself as just another man and no one special despite his extraordinary abilities; an example being the time he performed the Sun Breathing's forms for Suyako at her request and almost seemed embarrassed afterwards. Yoriichi was also noted by his brother to always have had faith in the future and was confident that despite the immense power of the Demon Slayers after they started using Breathing Styles, a generation would emerge that would surpass their own.

Overall Abilities: Yoriichi is the strongest Demon Slayer in history, being born with the Demon Slayer Mark, access to the Transparent World, and Selfless State, as well as possessing a physique polished to the highest caliber and innate swordsmanship talent. As a seven-year-old child who has never picked up a sword before, he was able to defeat a trained sword instructor effortlessly and he was referred to as a miraculous prodigy beyond compare. After training as a Demon Slayer, Yoriichi could defeat multiple demons to where his older brother stated that he as a child couldn't even compare to him as an adult.

He alone among the Demon Slayer Corps was able to corner Muzan Kibutsuji and overpowered him in an instant, having him on the verge of death until he barely managed to escape. Despite having avoided death, Muzan was deeply scarred by that encounter, referring to him as the true "monster" between the two of them, and even the sight of his earrings made him tremble in shock, while mere memories of Yoriichi caused the bodies of other demons who have never met him to tremble.

Yoriichi is a tall man with a lean muscular build, fair skin, maroon eyes, and long spiky hair with red tips that he kept in a ponytail. He has a similar overall appearance to his twin brother Michikatsu, but unlike him, he was slightly more slender, had shorter bangs, and wavier hair than him. Yoriichi is mostly expressionless, though sometimes a little solemn and aloof.

Yoriichi wore a red haori over a very pale orange-colored nagagi kimono with a black umanori-styled hakama, a pair of zōri with red straps and white tabi socks, with a Nichirin Sword carried at the left side of his waist, conventional to most Demon Slayers. He sported hanafuda earrings created by his mother as charms when he was thought to be deaf; he later gave them to his friend Sumiyoshi Kamado, who then passed the earrings down to his descendants and eventually Tanjiro as well.

Michikatsu is reserved, silent, and aloof, maintaining an aura of unnerving tranquility and mystery. It is revealed that Michikatsu harbored an immense sense of envy towards his younger twin brother for his natural talent and incredible abilities. These feelings of jealousy and contempt only became stronger upon seeing his brother become a peerless warrior of unmatched caliber among even the Demon Slayer Corps, with none of the Hashira coming close to his level of strength.

Michikatsu wears a purple-and-black hexagonal patterned nagagi kimono and black umanori-styled hakama pants tied with a white uwa-obi. He carries a katana at his waist. His eyes had dim purple irises and normal, white sclera as a human. As a child, he was normally seen wearing a white kimono as opposed to the purple-and-black patterned one he's seen wearing as an adult.

As a Demon Slayer in the golden era, his swordsmanship was already outstanding as he learnt them from Yoriichi himself and later stated that their techniques were so refined and legendary that they have no hopes of it being passed down for future generations. Michikatsu is the second strongest demon slayer after Yoriichi. Michikatsu uses Moon breathing due to being unable to learn Sun breathing from his younger brother, Michikatsu is more possessive than his brother.