Yoriichi Tsugikuni Yoriichi Tsugikuni 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, 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.