Aoi Tomosato is a member of the support staff for the Mobile Disaster Response Corps unit known as S.O.N.G., spending most of her time on the submarine command bridge that serves as the organization's mobile headquarters. She works alongside colleagues such as Sakuya Fujitaka and reports to the unit's commander, Genjuro Kazanari. Her role involves monitoring combat situations, managing information, and providing operational support to the Symphogear users in the field.

In terms of appearance, Aoi has dark blue hair and purple eyes, typically wearing a blue jacket over a blue dress with black tights and shoes. Her given name is written in hiragana, which can refer to the Japanese word for blue, while her surname uses the kanji for friend and village.

Aoi has a calm and composed demeanor, showing trust in her partners and the Symphogear wielders she assists during missions. She is professional and dedicated to her duties, handling tasks such as managing information leaks and contributing to strategic discussions about the Symphogear system's development and international political implications. Despite the serious nature of her work, she also shows a lighter side, appearing amused during lighter moments and even joining in celebrations with party poppers alongside Genjuro.

Throughout the series, Aoi serves as a consistent presence in the command center, helping to coordinate missions and keep the Symphogear users informed of developing situations. She is involved in key logistical operations, including the transport of important relics and artifacts, and helps explain technical matters and historical context to newer members of the team. Her role is primarily that of a support specialist rather than a frontline combatant, contributing to the team's effectiveness through her technical expertise and calm professionalism under pressure.