In a post-apocalyptic Tokyo, a mysterious girl known only as "Skull" wanders the streets wearing a mask made of bone. Her past is shrouded in mystery, and she rarely speaks to anyone. Despite her ominous appearance, Skull has a kind heart and uses her survival skills to help those in need.
As she navigates the dangerous ruins of the city, Skull encounters a group of survivors struggling to stay alive. They initially see her as a threat, but she proves her worth by helping them fend off attacks from raiders and scavenging for much-needed supplies. Gradually, Skull earns their trust and joins their ranks.
But the group soon discovers that Skull has a secret: she's searching for someone, some...