Yoriichi Tsugikuni

Yoriichi Tsugikuni is a major supporting character of Demon Slayer: Kimetsu no Yaiba. He is a legendary Demon Slayer who lived nearly 500 years ago during the Sengoku Era (the Golden Age of Demon Slayers), 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 Tanjiro Kamado and members of the Kamado Family. Yoriichi is the younger twin brother of Michikatsu Tsugikuni, who later became a demon and joined the Twelve Kizuki.