Aegis is an android created by the Kirijo Group; she is the last surviving model of their experimental anti-Shadow weapon. In combat, she uses a wide variety of high-tech weapons, from machine guns and rocket launchers to long range guns and “rocket punches.” Aegis has the highest durability of any of the characters, and her Personas focus on physical attacks.
Aegis is introduced during SEES’ summer beach vacation, where she is simultaneously the target of Mitsuru’s retrieval mission and Junpei’s “Operation Babe Hunt.” She immediately shows an instinctual interest in protecting the Main Character which even she cannot explain. Ikutsuki has her assigned to aid SEES, and she enrolls in Gekkoukan High to act as the Main Character’s bodyguard.
In the Persona 3: FES expansion, the player can access an epilogue to the main game called Episode Aegis (The Answer). There, Aegis replaces the Main Character as playable protagonist, inheriting his power to summon multiple Personas. The Main Character can also date Aegis in Persona 3: FES.
During her battle with Ryoji on the Moonlight Bridge, Aegis regains the memories trapped in her damaged circuits. The player learns that, ten years before the game, she was tasked to defeat or seal away Death so that the coming of Nyx would be averted. Since she was unable to defeat Death, she sealed the entity away in a young boy who was the sole survivor of a nearby car crash. That young boy was the Main Character. She is driven to protect him both to try and suppress Death and because she feels a great deal of guilt over her actions.
Aegis is damaged during her fight with Ryoji and must be repaired by the Kirijo Group. When she returns she shows more human-like qualities and emotions, and decides to stand against the power of Nyx with her friends in SEES. After the final encounter with Nyx, she is the only one who remembers Tartarus, the Dark Hour, and the Main Character’s sacrifice during his borrowed month of life. She allows him to live like a normal student for the few precious weeks that he has. Then, on Graduation Day, she holds the Main Character as he drifts into his final sleep, and swears that she will live her life protecting him.