Akira Hiiragi is the Governor of the artificial island known as Mermaid, where she serves as the founder and leader of Wärter, the island's peacekeeping force. In this role, she is the highest authority figure among the inhabitants, commanding respect from many who live under her governance. Akira is known throughout the island as its only male resident, a belief that grants her a unique and powerful position. However, this is a carefully maintained deception. Akira is biologically female, having been instructed by her mother to present as a man in order to remain safe. Her true gender is one of the island's most closely guarded secrets, known only to a select few such as Torino and Mirei until it is eventually exposed. This disguise is also a practical measure for survival, as her mother provided her with an artificial partner named Sri for her physical protection.

As a character, Akira is portrayed as benevolent and dedicated to bringing order and安宁 to the often chaotic environment of Mermaid. She carries the responsibilities of her position with a sense of duty, striving to guide and encourage the other residents of the island. Despite her authoritative role, she can display a shy or reserved side, particularly when confronted with the intimate dynamics of Liberator and Exstar relationships, known as Drive. Underneath her composed exterior, she also harbors a deep sense of personal longing. She has a romantic partner from before the Armed Virus outbreak, a person who never appears on screen, and she frequently thinks about this absent loved one, her body and memories retaining a powerful connection to her. This inner conflict is something she feels she must suppress in order to fulfill her duties as Governor.

In the story, Akira's role is primarily that of an ally and source of support for the main protagonists. She actively works to protect the residents of Mermaid, such as when she saves Kasumi and Hibiki from a gang on the beach. Her authority is demonstrated when she intervenes to prove Mirei's innocence to her own troops, overriding the orders of a subordinate. She also directly participates in combat when necessary. In one instance, when trapped in a building with terrorists, she is left with no choice but to kiss Mamori to achieve a necessary Drive transformation, successfully defeating their captors. This event, along with a moment where she sleeps next to Mamori and inspires her not to give up hope of leaving the island, establishes a close and supportive relationship with the main character. Her interactions with Mamori cause a flicker of jealousy in Mirei, hinting at a potential, though ultimately unrealized, complication in their dynamic.

Akira undergoes a significant revelation over the course of the series. The central pillar of her identity as the island's sole male is a lie, and the truth of her gender is exposed, forcing a public re-evaluation of her persona. As a resident of Mermaid, Akira is a Liberator, one of those infected with the A-virus. Her notable abilities are tied to this status. Like all Liberators, she can use a kiss to transform her partner, an Exstar, into a powerful weapon or form known as an Arm. For this purpose, she is partnered with Sri, the artificial Exstar provided by her mother. Her skills are sufficient to overcome armed terrorists in direct combat, demonstrating her competence as a fighter beyond just her political authority.