While each piece of media takes place in its own universe, they each focus around Black Rock Shooter, a mysterious black haired girl who possesses a burning blue eye and a powerful cannon that can shoot rocks at high speed.
The manga series, Black Rock Shooter: Innocent Soul, follows Black Rock Shooter and her serpent partner, Ron, as they venture the Hazama, a world between Heaven and Earth where stagnant souls that have had regrets become trapped.