Character who appears in Under Night In-Birth. He is an assassin who currently works for an unknown client. A long time ago, Seth's ancestors were one of the many families that fought among each other in Night Blade. He also has some connection with Linne, as he wishes to save her from her curse of reincarnation. To achieve this, he seeks out The Insulator who currently resides with Hyde, which leads to them clashing in the events of the story. While Hyde doesn't want to end Linne's life just yet, Seth insists that he ends her life as soon as possible.
