Setsuna/Story

Setsuna was a spirit in the Makai filled with an insatiable need to kill. When Shinnosuke Kagami opened the Hell's Gate, Setsuna escaped to the human world. Wandering about, Setsuna found the body of a infant in a battlefield and possessed it. His power made the body grow to adulthood. He slaughtered many until he decided to obtain himself a weapon. He finds Hibiki Takane's father, a master blacksmith, and orders him to make him a powerful, unbreakable sword. For eighty days, Hibiki's father wouldn't eat or sleep in order to create the blade. When he finished it, he passes away. Setsuna continues his massacre while beginning his search for the Sealing Maiden. He plans to kill her to keep Hell's Gate open and to ensure he would never have return to the Makai.

In his ending, he kills Kouryu and Yuki, leaving the gate open for others to come through (this is non-canon however).