Loki is the central protagonist of the anime, originally the Norse god of mischief and chaos. He was banished from the divine realm by the chief god Odin for his excessive pranks and exiled to the human world. As part of his punishment, Odin sealed Loki's power and trapped him in the body of a human child, giving him the appearance of a young boy with short brown hair and green eyes. In his true adult form, he appears as a tall young man with lighter hair. His childlike appearance belies his true nature as an ancient and powerful deity.

In terms of personality, Loki is intelligent, composed, and often displays a dry, sarcastic wit that suits his trickster origins. The anime version of his character is more reserved and serious compared to the manga, where he is depicted as more wild, silly, and mischievous. Despite his youthful form, he retains the cunning and manipulative instincts of a god, and he can be aloof and mysterious when dealing with others. He has a strong sense of pride and is initially dismissive of human concerns, though his experiences on Earth gradually make him more empathetic.

Loki's primary motivation is to return to the realm of the gods and regain his original body and power. To achieve this, Odin commanded him to collect evil auras, or supernatural entities that infest human hearts. This task requires him to operate a detective agency called the Enjaku Detective Agency, which specializes in paranormal mysteries. Solving these cases allows him to capture the auras and inch closer to his goal. Over time, his motivation shifts from simple self-interest to a deeper desire to protect those he has come to care about in the human world.

In the story, Loki serves as both the main character and the catalyst for most of the plot. He solves supernatural mysteries while navigating the constant threat posed by other Norse gods sent by Odin to assassinate him. His role evolves from a detached, solitary figure to a leader and protector who must confront the truth behind his exile and the looming prophecy of Ragnarok. His journey challenges his understanding of what it means to be a god and a friend.

Loki's key relationships include his loyal companion Yamino, who is actually his son Jormungand, the Midgard Serpent, disguised as a human man. Yamino is devoted to his father and serves as his assistant. He forms a close bond with Mayura Daidouji, a mystery-obsessed human girl who becomes his self-appointed assistant and eventually a true friend. She helps him see the value of human connections. Loki is also the father of Fenrir, a wolf-like son, and Hel, the ruler of the underworld. He has complex and often antagonistic relationships with other Norse gods such as Thor, Heimdall, and Freyr, some of whom are sent to kill him but later become uneasy allies.

Loki's development across the series shows him gradually softening toward humans and accepting his role as a father and protector. He begins as a god solely focused on his own return but grows to prioritize the safety of his friends and family. In critical moments, he is able to temporarily revert to his adult form when his power is restored, and ultimately he faces the truth of his exile and the fate of the divine world.

Notable abilities include his innate godly powers of illusion, deception, and magic. To compensate for his sealed strength, he wields a magical staff called Laevateinn, which he crafted himself, to channel his powers. He is a highly skilled detective with a sharp analytical mind. He also has a fear of deep water, a dislike of riding in cars, and an attraction to romantic interests, which humanize him despite his divine nature.