Izana Shinatose belongs to a genetically engineered third gender, biologically distinct from male or female, a common trait among Sidonia's population developed over centuries of space emigration. This biology permits transformation into male or female based on romantic attraction. Serving as Garde pilot trainee TS-291 and later promoted to Unit 723, Izana shows early competence in defense but lacks exceptional combat skills until undergoing significant physiological changes. After prolonged interaction with Nagate Tanikaze, Izana develops romantic feelings, triggering a biological transition into a female body. This results in distinct secondary sexual characteristics, including breast development and female genitalia, evidenced when standard flight suits no longer fit the altered physique. During combat against Gauna forces, Izana suffers critical injuries, losing her right arm and left leg. These are replaced with advanced prosthetics featuring a ten-fingered artificial hand that enhances dexterity for piloting. A neural interface is then integrated into her Garde unit, channeling sensor data directly into her brain via the prosthetic arm. This modification provides superior long-range detection capabilities, exceeding Sidonia's systems and specializing Izana for reconnaissance. Interpersonally, Izana forms a deep bond with Nagate, evolving from close friendship to romantic attachment, marked by pronounced jealousy towards others like Shizuka Hoshijiro or Tsumugi Shiraui interacting with him. Despite rivalry with fellow pilot Yuhata Midorikawa for Nagate's attention, they maintain a strong friendship, with Izana protecting Yuhata in combat at personal risk. Izana also develops a significant friendship with Tsumugi, assisting her in covertly exploring Sidonia despite regulations. Following Sidonia's colonization of the Lem star system and the defeat of the Large Mass Union Ship, Izana departs aboard a repaired Sidonia approximately ten years later with other crew members to seek new planetary colonies.