Pretty June refers to Jun, the swan-themed third fighter of the Science Ninja Team, who carries the designation G-3. Jun lost both parents in early childhood and was raised by an aunt, who also died during wartime. While fleeing the fighting, she took refuge in the mountains and came across an abandoned infant named Jinpei. She took responsibility for the child, and the two were later placed in an orphanage and grew up together like brother and sister. Their abilities eventually drew the attention of Doctor Nambu, who recruited and trained them for the team, and Jun became the third member at the age of sixteen. She is of mixed Japanese and American heritage, and in civilian life she runs the Snack J, a bar that serves as the team's informal meeting place and as her and Jinpei's home.

Jun is strong-willed, independent, and quick-witted, fitting the image of a modern young woman of her era. She is easygoing in daily life but takes her duties seriously and tries to look out for her teammates, and she has a sensitive, strongly maternal side. As the only female member of the team, she treats her position as entirely natural and never lets her gender define her capabilities. She is resilient and not given to brooding, yet she has a rich emotional life and often expresses appreciation for the beauty of the world the team fights to protect. Her motherly instinct is most visible in her relationship with Jinpei, whom she found as a baby and raised as a younger brother, and within the team she often acts as a quiet mediator, smoothing over disagreements and supporting the leader when tensions arise.

Jun's motivations are rooted in loyalty to her found family and a genuine commitment to protecting the world from the threats the team faces. Her sense of duty is matched by a desire to preserve the ordinary life she has built at the Snack J and the bonds she shares with her teammates, whom she regards as family.

In the story, Jun serves as the team's electronics and data specialist, handling communications, computer processing, and data analysis, and as their expert on explosives and hazardous materials. Her technical skills make her valuable in infiltration missions, disarming devices, and undercover work, where her intelligence and charisma help her obtain crucial information. In the third series, the team's battle continues against a renewed enemy as the conflict grows more intense, and Jun remains in her established role, providing the technical support and combat backup the team depends on.

Her key relationships define much of her character. With Jinpei she shares an almost maternal bond, acting as his guardian and protector. With the team leader Ken she carries an open but restrained affection marked by mutual respect, and she tends to support his decisions without being intrusive. Her bond with Joe carries a subtler attraction that becomes more apparent over the course of the story. Doctor Nambu acts as the mentor figure who discovered her, trained her, and guided her into becoming a fighter.

Jun develops from an orphaned child into a confident and capable heroine. Although she rarely receives the spotlight compared with her teammates, her growth is shown through her steady reliability, her deepening bonds with the others, and her willingness to risk herself for the team.

Her notable abilities include expertise in electronics, computers, and explosives, strong skills in hand-to-hand combat, and expert motorcycle riding. Her swan-themed birdstyle uniform grants her the power of flight or gliding, increased speed, strength, and endurance, and a visor that supplies tactical information. Her signature weapons are a wired yo-yo bomb, which can be used for direct attacks, entangling enemies, or timed demolition through a ring-triggered detonator, and feather-shaped shuriken. She can also perform the team's tornado technique, which becomes far more powerful when combined with the similar attacks of her teammates.