Sis, known as Onee, is a 32-year-old woman managing operations for the Eden of the East group. Though not an enrolled student, she has audited classes across various university departments. She serves as an assistant to the group's leader, Kazuomi Hirasawa, providing support and encouragement for his initiatives. Her unconventional erotic preferences unsettle the NEETs associated with Eden. She possesses the skill to operate semi-trucks, demonstrated when she spearheaded the hijacking of a truck carrying a Juiz supercomputer alongside Eden members Micchon and Takizawa during a critical incident in *Paradise Lost*. Sis remains a constant presence within Eden throughout the series and films, contributing to their missions.