"Kämpfer für die Liebe" centers on Natsuru Senou, an ordinary high school student whose life takes a dramatic turn when he is suddenly transformed into a female version of himself. This transformation is the result of being chosen as a "Kämpfer," a warrior enlisted to fight in a mysterious battle between individuals granted special powers. Kämpfers are divided into two factions: the Red Kämpfers and the Blue Kämpfers, who are locked in a perpetual conflict. Natsuru, now a female Kämpfer, is aligned with the Blue faction and must navigate the challenges of his new identity while engaging in battles against the Red Kämpfers.

The series explores Natsuru's struggle to adapt to his dual existence, balancing his male identity with his female Kämpfer form. His transformation is tied to a bracelet that triggers the change whenever he is drawn into combat. Natsuru's close friend, Shizuku Sangou, discovers his secret and becomes a key ally, offering support and guidance. Another significant character is Akane Mishou, a classmate who harbors feelings for Natsuru and is unaware of his Kämpfer identity. The dynamics between these characters are further complicated by the arrival of Mikoto Kondou, a fellow Kämpfer who initially appears as an antagonist but later becomes an ally.

As the story progresses, Natsuru uncovers the origins of the Kämpfer battles and the organization behind them, known as the Moderators. These enigmatic figures oversee the conflict and enforce the rules governing the Kämpfers. The narrative delves into themes of identity, loyalty, and the consequences of power, as Natsuru grapples with the moral implications of his role in the battles. The series balances action-packed fight sequences with moments of humor and introspection, creating a multifaceted exploration of its central premise.

The plot takes several twists as Natsuru and his allies confront increasingly formidable opponents, including rogue Kämpfers and those seeking to exploit the system for personal gain. The relationships between the characters evolve, with romantic tensions and rivalries adding depth to the story. By the conclusion, Natsuru must make critical decisions about his future as a Kämpfer and the impact of his actions on those around him. The series leaves room for interpretation regarding the ultimate resolution of the Kämpfer conflict, emphasizing the ongoing nature of the struggle and the personal growth of its characters.