Tsubasa began life as a parakeet cared for by Gorou Mutsumi after a wing injury. While recovering, she leapt from a window to show him her gratitude through flight, but her unhealed wing caused a fatal fall, leaving her with lasting acrophobia—a deep fear of heights.

Reincarnated as a guardian angel, she remembered her past life and her deep affection for Gorou. This devotion created friction with Rei, the Red Phoenix, who held romantic feelings for her despite having harmed Gorou. Starting as an Intermediate-rank guardian, Tsubasa dedicated herself fiercely to protecting Gorou, constantly honing her skills. Her persistent efforts led to a promotion to Senior rank in the second season.

Her personality mixed tomboyish energy with a feminine identity, marked by fiery loyalty reflected in her red motif. The name "Tsubasa," meaning "wing," directly recalled her avian past and the trauma that shaped her. After pursuing education, she worked as a newspaper deliverer, using a bicycle for both her job and personal travel.

Physically, she appeared as a teenage girl with shoulder-length blue-green hair and brown eyes, typically seen in a school uniform adorned with ribbons.