A legendary swordsmen who would a crimson blade, he is known as the creator of the original breathing style called sun breathing making him the predecessor of all breathing styles. He is the only one in the history giving the demon king Muzan Kibutsuji himself trauma if his defeat in mere seconds as wounds from his blade on anyone doesn't heal no matter what. He is also the brother of michikatsu Tsugikuni who goes ahead becoming the Uppermoon 1 for muzan, only because of jealousy