Birdy Cephon Altera, a vibrant law enforcement official of the Space Federation, gets marooned on Earth while on a quest for an extraterrestrial outlaw, Geega. Geega expertly manoeuvres his way into the fashion world, assuming a human form, which causes Birdy to join an undercover modelling agency using the name, "Shion Arita." Caught between her flourishing daytime modelling career and her nighttime pursuit of intergalactic criminals, Birdy finds herself swamped with work duties. On the other hand, a normal high school student, Tsutomu Senkawa, explores an unoccupied structure with his friend when Geega and Birdy chance upon the same location. Senkawa, a bystander, watches the conflict from afar, but Geega holds him hostage, and Birdy, unaware of the scenario, ambushes Geega. The resulting confrontation leads to Senkawa's accidental death, and in a desperate move, Birdy merges her soul with his to resurrect him. As a consequence of their fusion, Birdy and Senkawa share the same body, struggling to balance Senkawa's academic responsibilities, Arita's modelling career and Birdy's increasingly dangerous assignments as a Federation agent.