Eureka is a central character in the anime series 'Koukyoushihen Eureka Seven.' She is an enigmatic girl who pilots the Nirvash typeZERO, a powerful mecha. As a member of the mysterious organization known as Gekkostate, she plays a key role in the series' events. Throughout the story, Eureka struggles with her identity and relationships, particularly with Renton Thurston, the protagonist. Her journey involves discovering her past and the secrets behind her existence, ultimately leading to pivotal changes in the world and relationships around her.