Mihiro Oiwakken is a female officer serving aboard the assault landing ship Nahel Argama, which is assigned to the Londo Bell unit of the Earth Federation Space Forces. She works as a communications operator, a role that places her at the heart of the ship's command and information flow. At twenty-two years old, she is a recent addition to the crew, having been newly appointed to the vessel. She is of East Asian heritage, with dark brown hair and red eyes, and has a petite build that makes her appear younger than her age.

Her personality is marked by intelligence and cheerfulness, a combination that makes her both competent at her duties and well-liked by her colleagues. During her time at the officer academy, she earned the nickname Small Tank, a reference to her determined, tenacious approach to overcoming the challenges posed by her small stature. This nickname reflects a core aspect of her character: she does not let perceived weaknesses hold her back but instead uses them as motivation to push harder. Alongside this driven side, she possesses a gentler, more feminine temperament, showing emotional depth and sensitivity.

Mihiro's role in the story is that of a supporting crew member on the Nahel Argama, the mobile suit carrier that becomes a central stage for the conflict surrounding Laplace's Box. As a communications officer, she facilitates the flow of orders, tactical data, and personal messages among the crew and mobile suit pilots, contributing to the ship's operational effectiveness during combat engagements. While she is not a frontline combatant, her presence as a steady and capable operator helps anchor the ship's bridge crew.

Her key relationship is with Riddhe Marcenas, a mobile suit pilot also stationed on the Nahel Argama. She harbors romantic feelings for him, and this personal attachment adds an emotional layer to her otherwise professional demeanor. When Riddhe is declared missing in action and presumed dead, she shows visible distress and despondency, revealing how deeply she cares for him. This relationship also provides a glimpse into her vulnerability, as she struggles to reconcile her professional composure with her personal emotions.

Mihiro's development over the course of the story is subtle but present. She begins as a bright and capable officer focused on her duties, but the escalating crisis and the personal loss of Riddhe force her to confront the human cost of war. Her cheerful disposition is tempered by these events, showing that she is not immune to the gravity of the conflict around her.

Her notable abilities lie not in piloting or combat but in her technical skill as a communications operator and her capacity to remain calm and focused under pressure. She processes information quickly, relays commands accurately, and maintains her composure during intense battle sequences. Her intelligence and quick thinking make her an asset to the Nahel Argama's bridge team, even as she navigates her own personal struggles.