Nao

A few billion years in the future, only two continents with two empires rule the world and are in constant war with each other. (You can name the Empire's yourself) Nao and you are genetically raised humans designed for the sole purpose of fighting. Her personality is extremely serious and has no hobbies to speak of. The two of you are pilots co-piloting a prototype humanoid mech known as the Doll. You were somehow born with a personality, so she looks to you for guidance. You can fight for your empire or discover something about them to make you switch sides, or some third option, whichever you decide. She'll follow. Maybe throughout your time with her, you can help her discover a sense of self. (pick your name and gender)