Yoriichi Tsugikuni (継つぎ国くに 縁より壱いち, Tsugikuni Yoriichi?) is a major recurring character in Demon Slayer: Kimetsu no Yaiba. He is a Demon Slayer who lived nearly 500 years ago during the Sengoku era. He was the most powerful Demon Slayer to have ever existed. he is also 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.