Junko Tama is a central supporting character in the 1970s Japanese television series featuring the hero Kamen Rider V3. She is introduced as an ordinary young woman whose life becomes intertwined with the protagonist, Shiro Kazami, after a fateful encounter with the evil organization Destron. While attempting to flee from Destron monsters who discovered her spying on their secret base in the mountains, Junko nearly collides with Shiro on his motorcycle. After she faints from shock, he brings her to his family home for safety. This act of kindness tragically leads Destron to their doorstep, resulting in the murder of Shiro's entire family, a disaster for which Junko feels a deep and lasting sense of responsibility.

Possessing a personality marked by kindness, naivety, and a resolute courage against evil, Junko is a deeply caring individual who is driven by guilt and a desire to help Shiro in any way she can. Despite Shiro's frequent coldness and attempts to push her away, motivated by his fear of placing another person in danger, Junko persists in her support. Her determination is unwavering, and she eventually succeeds in becoming a close and trusted friend to the otherwise isolated hero. Her motivations are purely selfless; she seeks to atone for the tragedy she feels she caused and to stand against the forces of Destron, refusing to remain a passive bystander.

Within the story, Junko serves multiple critical functions. She is a key figure in the Boy Rider Corps, a network of young supporters, acting as a communications officer and monitoring radio transmissions to aid V3's missions. In her civilian life, she works at a sporting goods store owned by Tobei Tachibana, an ally of the Kamen Riders, further integrating her into the fight against evil. Her most notable role, however, is as a frequent target for Destron. Her persistent investigative nature and connection to Shiro make her a recurring hostage, a situation that creates immense tension and often serves as the catalyst for V3 to enter a life-or-death battle to rescue her. Her younger brother, Shigeru, is also part of this world, and she acts as a protective older sister to him, though she often displays more anxiety than he does when danger arises.

Junko undergoes significant development throughout the series. Initially, Shiro treats her with a harsh distance, refusing to engage with her emotionally to shield her from his dangerous life. However, as the story progresses, his attitude softens considerably. He begins to speak with her more openly and value her presence, transforming their relationship from one of obligation to a genuine and deep friendship. This change highlights Junko's unwavering perseverance and her positive influence on Shiro's character. Her own journey is one of moving from being a guilt-ridden victim to a proactive, if still vulnerable, ally who refuses to be defeated by fear. While she does not possess superhuman powers, her notable ability is her steadfast spirit and her role as the team's communications expert, providing logistical and emotional support that is vital to the hero's success.