Brunhild appears in the arc "The King of Fairies," and in the routes of Joel, Vincent, and Leon. She also appears briefly in one of the season 6+ routes. 

Eress is a fairy that is introduced in Joel's route when he and the protagonist save her from frogs. Due to the temporary decrease of her magical power, she loses her memory and can only maintain her reduced form, causing her to be mistaken for a bug at first sight. Brunhild is Eress' true identity and form. Brunhild is the daughter of the Fairt King; King Oberon, and therefore a fairy princess. She and her father have a very deep and special bond, despite Brunhild being the King's 879th daughter. Brunhild is Oberons' favorite daughter, falling easily to dark magic once he believes that Brunhild is dead. 

Voice: Deeper, soothing, and elegant

Example (The deeper version)