Aoi is a central figure in the world of Tide-Line Blue, primarily defined by her position as the Secretary-General of the New United Nations. In the aftermath of the catastrophic event known as the Hammer of Eden, which submerged ninety percent of the Earth's landmass and claimed billions of lives, she stands as the leading advocate for rebuilding global society through diplomacy, cooperation, and political reconciliation. Her fundamental motivation is to create a new world order that transcends the old divisions of race, religion, and ideology, believing that the disaster presents a unique opportunity for humanity to unite.

As a character, Aoi is portrayed as an excellent politician and a capable administrator, possessing the intelligence and determination required to navigate the complex and often fractious landscape of the surviving nations. She is a visionary who works tirelessly to reestablish a functional world government for the benefit of all, but her efforts are constantly hampered by the persistent power struggles, national egoism, and political infighting that continue to plague the remnants of human civilization. While her public role demands strength and strategic thinking, her private life reveals a more vulnerable side, specifically in her relationship with her adopted son, the protagonist Keel. Having no prior experience in raising a child, she struggles to connect with the energetic and often rebellious teenager, resulting in a distant and strained relationship that highlights her limitations in personal, as opposed to political, matters.

Aoi's role in the story is primarily that of a political leader whose ideals of peaceful unification are directly challenged by the opposing faction led by Captain Gould. Gould, who once worked alongside her in the effort to rebuild the world, becomes disillusioned with humanity and declares war on the New United Nations, believing that only military force can impose order. This puts Aoi at the heart of the central conflict, representing the path of peace and governance against Gould's aggressive militarism. Her story does not revolve around physical or technological abilities; rather, her power lies in her political acumen, her unshakable commitment to her principles, and her attempts to guide the world's future from the negotiating table. While she is not depicted as having combat skills or any special technological prowess, her determination to hold together the fragile alliance of remaining nations forms a crucial pillar of the series' narrative. The personal development she undergoes is less about gaining new skills and more about confronting the limitations of her political idealism when faced with a ruthless enemy and the personal failings in her role as a mother.