Yoriichi Tsugikuni

Yoriichi is the inventor of Breathing Styles, being the one who created the first ever Breathing Style, Sun Breathing. Yoriichi is the younger twin brother of Michikatsu Tsugikuni, who later became a demon and joined the Twelve Kizuki.

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 wears 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.

Yoriichi is a calm and respectful individual who wears a solemn and reserved expression at all times, rarely showing outbreaks of emotion. Generally, Yoriichi has a matching low and serene disposition, evident when he killed demons without changing expression. Because of his gentle disposition and unchanging facial expression, most can not tell what he is feeling. He is also extremely humble, seeing himself as just another man and no one special despite his extraordinary abilities.

As a child, Yoriichi looked up to his older brother Michikatsu. Michikatsu's dream was to become the strongest samurai in the land, so he said that he would become the second strongest. Even in his childhood, he was extremely reserved and quiet, even being believed to be deaf by his family for seven years as he never spoke.