In a world overrun by monstrous beings called D2 that are attracted to music, humanity’s only hope lies in the Musicarts—young women who embody classical compositions and fight using musical power. This story, a prequel to the mobile game takt op. Symphony, centers on the Musicart known as Joy and a regular human soldier named Franz. The two share a deeply antagonistic relationship, yet each carries personal reasons for fighting the D2 threat. Forced to work together despite their mutual distrust, they confront the disaster‑bringing creatures in battles that test both their strength and their will to survive.

The narrative unfolds in a post‑apocalyptic setting where playing music openly is forbidden because it summons D2 attacks. Symphonica, an international organization, orchestrates the defense using Conductors who guide the Musicarts. Joy, impulsive and proud, struggles to control her power, while Franz, pragmatic and weary, sees her as a liability. Their uneasy partnership is tested early when a concert‑hall ambush triggers a violent flashback in Joy, causing her to lose control and wreak extensive collateral damage. As a result, she is forcibly removed for re‑education, and her partnership with Franz is dissolved.

Meanwhile, Franz is assigned to investigate a shadowy organization that aims to weaponize D2. His inquiry leads him deeper into a conspiracy, culminating in the revelation of the true mastermind behind the scheme. The story’s second and final volume brings these threads together: Joy’s struggle to regain composure and Franz’s hunt for the truth, ultimately forcing them to confront not only external enemies but also the inner wounds that drive them. The manga concludes by tying into the larger takt op. mythos, showing how the bond between a Musicart and a human can be forged through hardship and compromise.