Nagisa first appears as a waitress at the Marine House seafood restaurant, catching Ryuji's attention with her t-back bikini. Despite her sweet and innocent demeanor, she suffers from Dissociative Identity Disorder, with an evil alter ego named Yasha.
She is part of the Midnight Angels gang, led by her boyfriend Junya Akutsu. Her mental disorder stems from being raped by him in the past. Ryuji saves her life, helping her overcome her issues, and they eventually become a couple, remaining together in GTO.
In the manga, Nagisa Nagase is briefly seen as Ryuji Danma's attractive girlfriend while he is in graduate school. They initially met in the GTO prequel, Shonan Junai Gumi. When Eikichi Onizuka is too angry to teach, he contemplates behind his desk while students watch a lesson given by Nagisa through a videotape.
In the anime, Nagisa first appears during a conversation between Onizuka and Danma in a bar after Onizuka's interview. Onizuka tries to get close to her, but Danma intervenes, pulling him away and starting a fight for his inappropriate behavior towards Nagisa. She does not appear in the live-action adaptation.
In the Shonan Junai Gumi OVA (episode 4), Nagisa has long, straight dark hair and attends the prestigious Fujisawa Girls School. A Hanya tattoo appears on her back near her left shoulder when her alter ego Yasha surfaces, and she rides a black Kawasaki Eliminator motorcycle.
