Nina Fortner, originally born as Anna Liebert, is the younger twin sister of Johan Liebert. She is the only physically unharmed survivor of the night her parents were killed and her brother was shot in what initially appeared to be a botched burglary. After she and Johan disappeared, she was adopted by the Fortner family in Heidelberg and raised under the name Nina Fortner, with no knowledge of her original identity. She grew into a sweet, kind, hardworking, and intelligent young woman, studying law at university and practicing aikido. Her life remained peaceful until Johan contacted her on her twentieth birthday, leading to the murder of her adoptive parents and forcing her to confront her buried past.

Personality-wise, Nina is characterized by resilience, introspection, and deep emotional scars from her traumatic childhood. Despite her suffering, she retains a caring and empathetic nature, especially toward the vulnerable. Her primary motivation is to uncover the truth about her identity and her family’s dark legacy, as well as to stop Johan from continuing his path of destruction. She is primarily a pacifist but will threaten or use force when she believes it is necessary to protect others. Her journey is marked by a struggle between love for her twin and the horror of his actions, making her a psychological counterpoint to Johan.

Nina’s role in the story is central: she is both a key to understanding Johan’s past and a symbol of hope and recovery. She pursues Johan with different methods and reasons than Dr. Kenzo Tenma, driven by a personal need for closure and justice rather than solely guilt or responsibility. Her relationship with Johan is deeply complex—while he sees her as the only person who truly understands him, she views him as a destructive force that must be stopped. Her bond with Tenma becomes one of mutual trust and shared purpose, with Tenma serving as an ally and moral compass. She also develops a protective relationship with the boy Dieter, reflecting her nurturing side.

Throughout the series, Nina undergoes significant development. Initially suffering from amnesia due to psychological trauma, she gradually recovers her memories through hypnosis and direct confrontation with her past. It is revealed that she was the twin taken by Franz Bonaparta to the Red Rose Mansion, where she witnessed mass murder and was told to forget what she saw and run away. She was also the one who shot Johan in the head at his own urging after he killed their parents. This revelation reshapes her identity, transforming her from a traumatized victim into a proactive seeker of understanding and closure. By the end of the story, she has largely overcome her trauma, graduates from university, and plans to attend law school.

In terms of notable abilities, Nina does not possess supernatural powers. She is an adept practitioner of aikido, demonstrating agility and defensive tactics that she uses for self-defense rather than aggression. Her true strength lies in her psychological resilience, determination, and emotional depth—qualities that allow her to confront her brother and the horrors of her past without succumbing to despair. Her intelligence and resourcefulness also make her a key ally in the effort to stop Johan.