Hideyasu "Sōki" Yūki was a biological son of Ieyasu Tokugawa and a warrior who possesses the dark power of the Oni. He goes by many names besides Sōki and Hideyasu Yuki; Blue Demon and Oni of the Ash. Having Lamentation, his prized broadsword he learned about Hideyoshi's insidious scheme, he sets out on a journey to burn the Genma trees and defeat the Genma running rampant across the land.