"Dangaizer 3" is a three-episode OVA series that blends science fiction, mecha action, and supernatural elements. The story is set in a near-future Japan where a secret government organization, the Dangaizer Team, is tasked with combating supernatural threats using advanced mecha technology. The team operates the Dangaizer, a powerful combat robot designed to fight against monstrous entities known as "Demons," which are manifestations of negative human emotions and desires.

The protagonist, Yuka Minase, is a young woman who becomes the pilot of the Dangaizer after her brother, a former pilot, is killed in action. Yuka struggles with her grief and the immense responsibility of piloting the mecha, which requires a strong emotional and mental connection to operate effectively. Her journey is marked by personal growth as she learns to harness her inner strength and confront her fears.

The narrative introduces a rival organization, the Black Noir, which seeks to exploit the Demons for their own gain. This group is led by the enigmatic and manipulative Dr. Hazuki, who has a personal vendetta against the Dangaizer Team. The conflict between the Dangaizer Team and Black Noir escalates as both sides vie for control over the Demons and the technology used to combat them.

Key characters include Yuka's teammates, who provide support and camaraderie, and Dr. Hazuki's subordinates, who serve as recurring antagonists. The series explores themes of loss, resilience, and the ethical implications of using advanced technology to combat supernatural threats. The plot is driven by intense mecha battles, personal rivalries, and the psychological toll of confronting the Demons, which often reflect the darkest aspects of human nature.

The series concludes with a climactic showdown between the Dangaizer and the ultimate Demon, which tests Yuka's resolve and the limits of the Dangaizer's capabilities. The resolution ties together the personal and external conflicts, leaving a lasting impact on the characters and their world.