Sister, known to Eden group members as "Sis" or "Onee", functions as an overseer within the organization dedicated to an image recognition system and social networking project. She maintains a consistent presence across the series and films, primarily offering organizational support and encouragement to other members. At 32, she is older than most Eden companions. Her personality includes distinctive erotic interests that unsettle her younger NEET companions, yet she demonstrates enthusiastic support for the group's activities. She serves as an assistant to leader Kazuomi Hirasawa, often coaxing and motivating him. Her background involves attending classes across multiple university departments without formal enrollment as a degree-seeking student, contributing to her Eden role. In the film continuations, as Eden evolves into a formal business, Sister participates in critical missions, including a coordinated effort with Micchon to hijack a mobile command center (Juiz truck) during the missile crisis. Her documented contributions center on group dynamics within Eden's activities.