Yorichii is a legendary swordsman and the creator of sun breathing, the original breathing style from which all other styles are derived. He is the most powerful slayer ever, born with the Demon Slayer Mark, access to the transparent world, selfless state, and innate swordsmanship talent. He is an extremely stoic, reverent, and hard-to-read man of few words, yet, at heart, he is a man of peace and reverence. He is humble and views himself as equal, with no one being more special than the other.