Juli Bahana is a sixteen-year-old character who enters the story as a scholarship student aboard the Liebe Delta space station. As a member of the Zwei, an elite class of second-year students, she holds the highest academic rank and is recognized as the group's leader. Her background is marked by the absence of her parents, as she grew up in an orphanage, which has instilled in her a strong tendency to solve problems on her own without relying on others. A tall, beautiful girl with blue eyes and brown hair, she has a habit of playing with her bangs when she is troubled or thinking.

Her personality is defined by a calm, kind, and fair-minded demeanor, coupled with a quiet inner fortitude. Despite her intelligence and capability, she lacks the natural charisma typically expected of a leader, and she can be indecisive. She is deeply caring and has a strong maternal instinct, which is most visibly expressed in her attentive care for the young boy Pat Campbell, for whom she serves as a surrogate mother figure. One of her notable, more human flaws is her extremely poor fashion sense; she typically wears tracksuits or overalls with appliques, much to the dismay of her peers who see it as a waste of her beauty.

Juli is driven by a sense of duty and a desire to do what is right, having initially entered the space station on a scholarship to please her foster parents. Her primary motivation throughout the crisis is the survival and well-being of the crew. However, she also struggles with a tendency to put others before herself and to withdraw from the spotlight, which can make her vulnerable in high-pressure situations. During the initial chaos following the failure of the space station's dive, she became the de facto captain while an inept classmate, Lucson, held the title nominally. After the authoritarian Team Blue is overthrown, she is officially elected captain by majority vote. Her tenure is extremely stressful, as she struggles to maintain order and implement fair policies, such as abolishing a hated points system. The immense pressure and guilt following a deadly attack on the ship ultimately lead to her resignation from the captaincy.

Her most complex relationship is with Aires Blue, the leader of Team Blue. Despite the fact that he threatened her and effectively used her as a figurehead, she developed a special, romantic attachment to him during his rule. After his defeat, she keeps his bandana and privately admits to herself that she had fallen in love with him. She also maintains a professional and trusting relationship with Stein Heigar, her second-in-command, whose cold logic she often relies on, even as his methods become increasingly harsh. Her bond with the young boy Pat is a key part of her daily life, as she provides him with the nurturing care he needs after losing his father. As events spiral out of control and she loses her position, her development centers on confronting her own fragility, moving from a state of helplessness and self-blame to a point where she seeks to help others, including her fellow crewmate Kouji Aiba.

Juli does not possess any special combat or technological abilities. Her notable skills are entirely academic and administrative: she is a top-tier student and a strategic planner who thinks carefully before acting. Her primary ability is her calm judgment and mental resilience, which allows her to maintain a level head during a coup and send out repeated SOS messages, even when most others are panicking. However, her ultimate vulnerability is that her innate intelligence and kindness are not sufficient substitutes for the forceful charisma and decisiveness required to control a ship full of desperate students under extreme duress.