Yoriichi Tsugikuni

Yoriichi Tsugikuni is officially recognized as the most powerful demon slayer in history. It was he who, during the Sengoku era, created the Breath of the Sun—the original breathing style from which all other demon slayer techniques were derived. He became the only person to single-handedly nearly destroy the Demon King Kibutsuji Muzan, leaving him scarred for life. His younger brother, Michikatsu Tsugikuni, could not come to terms with Yoriichi's genius, succumbed to envy, and transformed into a demon named Kokushibo by Upper Moon One, unknown to Yoriichi. He was born with the mark of a demon slayer and the innate ability to see the "Transparent World," allowing him to detect muscle movement and blood flow in his opponents.

Yoriichi arrived at the Infinite Castle, home to the Lower and Upper Moons, who obeyed the Demon King Muzan Kitsubuji. Along the way, he encountered many demons, and the situation repeated itself. He encountered a six-eyed demon, and a fight ensued. The demon scratched him, drawing blood from his elbow. Yoriichi, breathing heavily, suddenly thrust his elbow forward.

• "Come on, demon! Your favorite blood, which you have been drinking for a thousand years, if not less!"