Freyr is a god from Asgard who appears in the human world, known as Midgard, as a recurring character. He is recognizable by his tall, lean build, brown hair, and blue eyes, and he typically presents himself as a young man in his mid to late twenties, despite being thousands of years old. In the human world, Freyr adopts the flamboyant persona of the Phantom Thief Freyr, a role he embraces with immense theatricality and showmanship.

Freyr’s personality is defined by a peculiar mix of divine power and comedic obliviousness. He is a ditz, often referred to alongside his sister as one of the "stupid siblings" due to his lack of common sense and tendency to get confused easily. He is incredibly self-absorbed, paying little attention to matters that do not directly interest him, and has a famously short attention span. Despite this, he is immensely optimistic and possesses an unwavering conviction; once he decides on a goal, nothing can dissuade him. He has a deeply romantic and imaginative nature, which fuels his desire for convoluted and dramatic plots. This is most evident in his decision to become a phantom thief purely because his rival, Loki, was acting as a detective.

His primary motivation upon arriving in the human world is twofold. Officially, he teams up with the god Heimdall to prevent Loki from returning to Asgard and to protect his sister, Freya, whom he fears may be corrupted by the trickster god. However, his personal mission shifts dramatically the moment he encounters Mayura Daidouji, Loki’s human assistant. He falls in love with her at first sight, declaring her to be the perfect woman and calling her Yamato Nadeshiko, a term for the ideal Japanese woman. From that point on, his actions are largely motivated by his desire to win Mayura's heart, a pursuit she remains largely oblivious to.

Within the story's narrative, Freyr serves as a comedic rival to Loki. Their conflict is often less about genuine malice and more about playing the roles of detective and phantom thief. In a notable early scheme, Freyr creates a puzzle for Loki by stealing items with the first letters of their names spelling out L-O-K-I. His most significant relationship is with his sister, Freya. He is intensely protective of her, and his serious concern for her safety is one of the few things that can momentarily pull him away from his airheaded pursuits. Once he confirms she is safe and happy, however, he quickly returns to his own interests. He also has a working relationship with Heimdall, acting on his orders for a time, though Freyr's personal goals often take precedence.

Freyr shows little to no serious character development in the traditional sense, remaining a static and humorous figure for most of the series. While there are hints at a more serious and capable warrior beneath the surface, these moments are fleeting and never last. His core identity as a lovable, optimistic, and distraction-prone god remains consistent.

Despite his foolish demeanor, Freyr possesses notable abilities befitting a god of his stature. He is a highly skilled warrior and is recognized as the best among the gods in the use of Runes, with even Loki admitting that Freyr surpasses him in this area. His most unique talent is a creative form of invention that relies entirely on his imagination; the more imaginative the idea, the more effectively the invention functions, powered by his divine energy. This creative skill is demonstrated by his signature vehicle, Gullinburst, a flying mechanical pig that he uses in his capers as a phantom thief. He is also a formidable swordsman and warrior, a reputation he earned as a hero among the gods.