Miyuki Kodai is the daughter of Susumu Kodai and Yuki Mori. Being born from parents within the Earth Defense Force, she never got to spend time with either of her parents for very long; as a result, she lacks the connection that most children has, although she looks up to her mother moreso than her father.
During the 2220 incident where Yuki was presumed dead, Miyuki was disappointed by her father, whom she deemed selfish and blames him for her mother's death. She worked for Dr. Sado's animal hospital, and during her father's mission to protect the third emigration fleet, she admits that she failed to see why her father was an icon when all he cared about is the Yamato and how he can save everybody but her mother. Upon the final hour of the evacuation from Earth away from the Cascade Black Hole she was put on the life boat by Analyzer on Dr. Sado's orders when she heard that he will be staying on Earth. On the way to evacuation site, her life boat was struck by lightning that disabled the vehicle. Hearing that her life boat did not reach its destination, Kodai boarded his Cosmo Zero and flew in search of the wreakage. Upon finding the ruins, he rescued her from the debris and took her up along with the other survivors on the Yamato. This action helped her change her point of view, as she suddenly realized that he would do anything to save someone.