Aki is the protagonist of the story, a young girl who belongs to the generation born after the societal collapse known as Red Day, an event that occurred thirteen years prior to the start of the narrative when a deadly disease wiped out ninety percent of humanity, causing the dead to rise as zombies. Because of this, she has no direct memory or firsthand experience of the world that existed before the catastrophe. She grew up in a small, isolated village where the surviving human population lives in relative safety, separated from the zombies that roam the outside world.

Personality-wise, Aki is described as being vivacious and determined, possessing a spirited drive that pushes her to take action. Her primary motivation is a deeply personal one: she leaves the safety of her village to search for her missing father. Her father had left the village sometime in the past, and his disappearance serves as the emotional catalyst for her journey.

In the story, Aki takes on the central role as the leader of the main group. Her decision to find her father is what kicks off the plot, and she is accompanied on this dangerous quest by her two close childhood friends, Natsuki and Haru. Her key relationships are initially defined by this tight-knit trio. As the journey progresses, the group encounters and rescues two other survivors, a knowledgeable girl named Yū and a kind-hearted girl named Sakura, who then join Aki's party, expanding the core cast. While the source material for the anime has been noted to have limited character development for its main cast, Aki remains the focal point around which the narrative and the group's dynamics revolve.

Regarding her abilities, Aki is capable of defending herself in a world overrun by zombies. Her primary weapon is distinctive and practical for a post-apocalyptic setting: a modified saw. This choice of weapon reflects the resourcefulness required to survive, as it is likely a repurposed tool adapted for combat against the undead. She possesses the necessary combat skills to fight and survive, a trait common among her generation, which has been raised in this dangerous world.