Parakeet Tsubasa was born on May 4, 1987, as a bird later identified as a parakeet. She suffered injuries from unknown causes and was found outdoors by a young boy, Gorō Mutsumi. An unnamed girl passing by helped Gorō treat the parakeet's wounds. Gorō then named her "Tsubasa" after the helpful girl, planning to care for her until she could fly again. Despite severe wing injuries, Tsubasa attempted flight in response to Gorō's wish for her to soar, resulting in a fatal fall where she struck her head.

After death, she became one of twelve guardian angels protecting Gorō Mutsumi, specifically returning as the fifth. Red serves as her designated image color. In this angelic role, she was also selected as one of the Four Saint Beast brides, designated as the bride for Rei.

Tsubasa possesses an easy-going personality. She demonstrates loyalty and supportiveness towards close friends, readily assisting them when they encounter trouble. Her kindness includes discernment, reserving respect primarily for those within her trusted circle. She exhibits a strong aversion to being controlled and rejects forced romantic advances. A persistent fear of heights stems from her traumatic death. Her interests encompass singing and dancing. She occasionally engages in conflicts, notably trading insults like "blue haired chicken" and "old maid" with the angel Mika, and clashing with Kurumi over food. Her relationship with the cat angel Tamami is complex; despite a general dislike of cats, she sometimes tolerates Tamami's company. She consistently maintains a positive friendship with Ran.

Characterization varies across media. The manga highlights more tomboyish traits and her enjoyment of sports activities like jogging. In the second anime season, she acquires a part-time job delivering newspapers after school using a bicycle, which also becomes a personal enjoyment. Her physical measurements shift slightly between seasons: Bust/Waist/Hip transition from 80/57/84 cm in Season 1 to 82/56/82 cm in Season 2.