"takt op. Destiny" is set in a dystopian future where Earth has been overrun by monstrous creatures known as D2s, which are drawn to and destroy music. Humanity has been forced to abandon musical expression to survive, as the D2s are attracted to sound. In this world, a group of individuals known as Conductors and their partners, called Musicarts, fight to protect humanity. Musicarts are humanoid beings born from classical music scores, wielding extraordinary powers tied to their musical origins.

The story centers on Takt Asahina, a young Conductor who forms a bond with Destiny, a Musicart born from Beethoven’s "Symphony No. 5." Takt is driven by a deep love for music, despite the dangers it poses in this world. Destiny, on the other hand, is a stoic and powerful warrior who fights alongside Takt to combat the D2s. Their partnership is complicated by Takt’s impulsive nature and Destiny’s mysterious past, which gradually unfolds as the series progresses.

As Takt and Destiny journey across the United States, they encounter other Conductors and Musicarts, each with their own motivations and struggles. The narrative explores themes of sacrifice, the enduring power of music, and the human spirit’s resilience in the face of adversity. The relationship between Takt and Destiny evolves as they confront both external threats and internal conflicts, revealing the emotional and psychological toll of their mission.

The series balances action-packed battles with quieter, character-driven moments, delving into the personal histories of its protagonists and the world they inhabit. The overarching plot involves uncovering the origins of the D2s and the true nature of Musicarts, as well as the possibility of restoring music to humanity. Through its blend of fantasy, drama, and music, "takt op. Destiny" presents a story that intertwines the beauty of art with the struggle for survival in a hostile world.