Musica is one of three triplet sirens serving the Zor, a nomadic humanoid alien race returning to reclaim their ancestral homeworld, Glorie, from human colonists. Alongside her sisters Musiere and Muselle, she inspires the Zor people through music. During the conflict between the Zor and the Southern Cross Army protecting Glorie, Musica begins questioning her people's motivations and methods. This internal conflict leads her to defect from the Zor mothership after encountering Bowie Emerson, a human soldier and pacifist musician serving in the Southern Cross Army's 15th Squad.

Musica defects to Glorie, where she and Bowie develop romantic feelings for each other. They flee together into the wilderness to evade capture by Southern Cross military police officer Lana Isavia. Her defection and alignment with the humans mark a significant shift in loyalty, rejecting her original role supporting the Zor reclamation war. Musica's actions help bridge understanding between humans and Zor, though her ultimate fate remains undisclosed.