Jun Fudou, the protagonist of Devilman Lady, exists in two primary versions with distinct backgrounds. In the original manga, she is a former Olympic-level athlete who works as a school teacher, known for her sophisticated and good-natured personality. In the anime adaptation, she is reimagined as a 22-year-old supermodel who is shy, introverted, and deeply sensitive, often struggling with feelings of emptiness despite her professional success. Her transformation into the Devilman Lady, a being that retains human consciousness within a demonic body, is triggered by extreme stress or a violent encounter with a Devil Beast. The manga version endures a brutal assault during a school trip, while the anime version is deliberately put in harm's way by the enigmatic agent Lan Asuka, who then forces Jun into service with the secret organization known as the Human Alliance.

Regardless of the iteration, Jun is a reluctant warrior whose core motivation is the protection of others. She is compelled to hunt rogue Devil Beasts, mutated humans who have lost their sanity to a condition called Devil Beast Syndrome. Her role in the story is that of a tragic hunter, forced to destroy beings that were once human, which causes her intense psychological distress. Her personality in human form is often defined by her self-loathing and quiet demeanor, which contrasts sharply with her transformed state. As the Devilman Lady, she becomes more aggressive, instinctive, and violent, tearing enemies apart with claws and demonic power. Despite this ferocity, her fundamental sense of right and wrong remains intact, thanks in part to special enzymes administered by her scientist father in the manga. The anime delves even deeper into the duality of her existence, portraying her Devilman persona as a lustful and temperamental force that Jun both fears and relies upon, leading to severe bouts of self-loathing and a struggle to maintain her sanity.

Key relationships define her journey. Her partnership with Lan Asuka is central and complex; Lan acts as a cold, demanding handler who is also deeply attracted to Jun, creating a dynamic of control, dependency, and undercurrents of romantic tension. This relationship is contrasted by her pure and nurturing bond with Kazumi Takiura in the anime, a younger model who looks up to Jun. Kazumi represents Jun’s last shred of humanity and a source of unconditional affection, making her eventual fate a pivotal point of trauma for Jun. Her relationship with her male predecessor, Akira Fudo, is also significant; after meeting him in Hell, she falls in love with him, and her devotion to him remains a powerful, though mysterious, force in her life. Her encounters with Devil Beasts who were once close to her, such as her childhood rival Aoi Kurosaki who harbors obsessive feelings for her, further deepen her tragedy.

Jun undergoes a profound and harrowing character arc. She begins as a passive individual controlled by circumstances and by Lan Asuka but gradually loses nearly everything her identity is built upon, including her home, her career, and her loved ones. This process of relentless loss forces her to grow more independent and powerful, culminating in a final confrontation where she rejects Asuka's control. In this ultimate battle, she embraces her monstrous power, achieving a giant "Giga" form, and severs her ties to her former human life, lamenting that she can never be human again.

Her notable abilities as the Devilman Lady include superhuman strength, speed, agility, and a potent healing factor. She possesses sharp claws and can sharpen the wing-like appendages on her head into blades known as a Devil Cutter. She has the power of flight, using wings that sprout from her back, and can discharge high-voltage electricity from her body as a Devil Beam. Her most formidable power is the Giga Effect, which allows her to grow to a colossal size, becoming a towering, blue-skinned demon of immense destructive capability.