Birdy the Mighty

Plot Synopsis

Tsutomu, a formerly normal high school boy, finds himself caught in the crossfire between a criminal and the alien supercop Birdy. After accidentally killing Tsutomu when the criminal used him as a shield, Birdy merges his soul into her body in order to save his life until his body can be repaired, and the two begin adjusting to their new double life, as they must now juggle maintaining Tsutomu's daily life as well as Birdy's missions.

How is it plural?

Throughout the series, Tsutomu's consciousness exists implanted into Birdy's body, and the two coexist via shapeshifting and internal communication to keep up appearances, with Tsutomu taking the front during day to day activities, and Birdy fronting to handle her police duties. While the two initially fight constantly, they gradually begin to work more effectively as a team. Different adaptations and sequels delve into this connection to varying extents, with the most extensive including representations of dormancy and hints of in-system romantic attraction / relationships.