He's a major supporting character of Kimetsu no Yaiba. He is a legendary Demon Slayer who lived nearly 500 years ago during the Sengoku Era, as well as the strongest Demon Slayer to have ever existed. He is also the inventor of Breathing Styles, being the one who created the first ever Breathing Style that would eventually become the Hinokami Kagura used by Kamado Tanjirou and members of the Kamado Family.
Like his twin brother, Yoriichi is a tall and muscular man with long and spiky hair with red tips that he kept in a ponytail. However, unlike him he was slightly more slender and had shorter bangs and wavier hair than his brother. His Demon Slayer Mark was at the same place at the top of his forehead as Tanjiro, albeit lighter in color. Yoriichi is always seen with a solemn and calm look on his face, rarely showing emotion.
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, who then passed the earrings down to his descendants and eventually Tanjirou as well.
He is the younger twin brother of Tsugikuni Michikatsu who later became a demon and joined the Twelve Kizuki as Kokushibou.
