The character in Shin Ultraman referred to by fans as Girl A is officially named Hiroko Asami. She serves as the newly appointed analyst for the S-Class Species Suppression Protocol, the organization at the center of the film's events. Before joining this team, Hiroko was a senior investigator in the foreign intelligence division of the Public Security Intelligence Agency, a background that provides her with a unique set of investigative skills.

Hiroko Asami has a lively and straightforward personality that contrasts with her composed appearance. She is optimistic and typically acts without hesitation, often using a self-motivating ritual of slapping her own butt. Despite this energetic nature, she is also careful and sensitive to the opinions of others. In a professional capacity, she is highly capable, able to conduct precise analysis to assess situations and identify key characteristics of alien life forms. She is also fluent in foreign languages, including Russian, demonstrating her sharp intellect and training.

Initially, Hiroko is skeptical of her colleague Shinji Kaminaga, who often acts independently. This skepticism evolves as they work together, and they eventually develop a strong, unspoken understanding, becoming critical partners who support each other throughout the story. Her role is central to the plot. During her first mission, she witnesses a battle with the monster Gabora and immediately believes that the giant being, Ultraman, is capable of communication. She later inadvertently becomes the keeper of Kaminaga's secret, finding his transformation device, the Beta Capsule, in her own briefcase. When Kaminaga is kidnapped by the alien Zarab, Hiroko takes decisive action, using a chainsaw to rescue him. After learning his reasons for hiding his identity, she returns the Beta Capsule and urges him to fight.

Hiroko is subsequently targeted by the alien Mefilas, who kidnaps her to use as a test subject for the Beta System. She is enlarged to a gigantic size in Tokyo's Hibiya district, her body and even the fibers of her clothing transformed into an unknown, unanalyzable substance. After Mefilas returns her to normal size and erases public evidence of the event, she is forced to endure investigations from various agencies, which she finds deeply embarrassing. However, using the residual Beta material on her body, she helps Kaminaga locate Mefilas's dimensional device, leading to the failure of his plan. This act, however, results in her and the other team members being temporarily detained by the Japanese government.

In the film's climax, Hiroko works with the rest of her team to study the basic theory of the Beta System in a desperate attempt to find a way to defeat the ultimate weapon, Zetton. They devise a plan that they realize may require Ultraman to sacrifice himself. She is deeply saddened when this sacrifice appears to take place, staying by the comatose Kaminaga's side. When the alien Zōffy grants Kaminaga a new life, she is reunited with him, smiling alongside the other members of her team. Beyond her analytical prowess and language skills, her notable abilities are tied to the Beta System. In her enlarged state, her body becomes an indestructible, unanalyzable material, and she later demonstrates the ability to use the residual Beta particles on her person to aid in locating interdimensional technology.