Rina Takaoka arrives as a cold and dismissive transfer student, rebuffing classmates like Natsuki Kisumi due to her guarded nature. She comes from Jotoh Academy, known for intensive martial arts training, but avoids combat sports after a traumatic incident. This event involved a wrestling match with her then-boyfriend, Keiji Muto, where she was manipulated into fighting him at full strength despite his prior injury inflicted by Jotoh associates under Kyotaro Himuro's orders. Keiji's severe injuries led Rina to blame her martial arts skills for loss and pain, causing her withdrawal from wrestling and distrust of others.

Her expertise is in catch wrestling, focusing on joint locks, holds, and throws to efficiently immobilize opponents. She displays exceptional skill, easily overpowering multiple Jotoh assailants seeking retribution and neutralizing adversaries like Naoya Hondo. She holds her own against fighters like Natsuki. Initially, she views her abilities as a curse due to the Keiji incident, believing martial arts bring misfortune.

Rina is an avid motorcyclist whose Honda NS 400 R represents her independence. The motorcycle's destruction by Jotoh agent Tetsuo Daigo, framed as Natsuki's act, reignites her distrust and triggers a confrontation with Natsuki. After Daigo reveals the truth about both Keiji's injury and the sabotage, Rina recognizes Natsuki's genuine support. This allows her to start reconciling with her past, gradually accepting martial arts can be practiced without causing harm and that camaraderie is possible. She later risks herself to aid Natsuki in a critical battle against Akira Kandori, a formidable judo champion and Jotoh enforcer, marking her shift from isolation to loyalty.

Her development culminates in embracing her role as Natsuki's ally and friendly rival, moving past her trauma to find renewed purpose in martial arts focused on self-improvement and mutual respect.