"Ragnarok - Matantei Loki" is a supernatural mystery anime based on the manga by Sakura Kinoshita. The story centers around Loki, the Norse god of mischief, who is exiled from the divine realm of Asgard by Odin for his disruptive behavior. Stripped of his divine powers and transformed into a child, Loki is sent to the human world to live among mortals. His mission is to solve 100 cases of supernatural phenomena to atone for his past actions and earn his way back to Asgard.

In the human world, Loki establishes himself as a detective, operating under the guise of a young boy. He is accompanied by Yamino, his loyal servant and fellow Asgardian, who takes on the role of his caretaker. Together, they investigate mysterious occurrences that often involve other gods, mythical beings, or supernatural forces. These cases frequently tie back to the machinations of other exiled gods or entities seeking to disrupt the balance between the human and divine realms.

The narrative introduces a variety of characters, both human and divine, who become entangled in Loki's investigations. Among them is Mayura Daidouji, a high school girl with a strong interest in the occult, who becomes an unwitting ally to Loki. Mayura's curiosity and determination often lead her to assist in solving cases, despite her initial skepticism about the supernatural. Other key figures include Heimdall, another exiled god who becomes a rival to Loki, and Freya, a goddess with her own agenda who occasionally aids or hinders Loki's progress.

As the series progresses, the overarching plot delves deeper into the conflicts between the gods and their influence on the human world. Loki's investigations reveal a larger conspiracy involving the manipulation of human lives by divine forces, as well as the personal struggles of the gods themselves. The series balances episodic mysteries with an evolving narrative that explores themes of redemption, loyalty, and the complexities of divine intervention in mortal affairs.

The anime maintains a focus on the interplay between the supernatural and the mundane, blending elements of Norse mythology with a detective framework. Through its episodic structure, "Ragnarok - Matantei Loki" weaves together individual cases with a broader storyline, gradually uncovering the motivations and fates of its characters while keeping the central mystery of Loki's exile and redemption at its core.