In another world, the eponymous Black Rock Shooter battles a mysterious red-eyed opponent. Meanwhile, in the human world, Mato Kuroi enters middle school and takes an interest in her classmate, Yomi Takanashi. The two quickly become friends due to their common fondness for a book from their childhood. After inviting Mato to her house, Yomi becomes worried when Kagari Izuriha, a wheelchair-bound girl who wants to keep Yomi to herself, arrives and acts with hostility towards Mato, causing her to become frightened. Meanwhile, in the other world, Black Rock Shooter follows a green trail to a wasteland filled with broken toys where she is attacked by a girl resembling Kagari named Chariot.

As Strength prepares to sacrifice herself in order to stop Yuu, Mato becomes determined to stop Black Rock Shooter from killing her. She ends up inside a blue world, where she herself is Black Rock Shooter, standing against Insane Black Rock Shooter. As Kagari and Arata also recover their painful memories, the revived people of the other world combine their strengths to give Mato the power to defeat Insane Black Rock Shooter, uniting the world as one. Upon regaining herself, Mato finds Strength in a weakened state, who assures Yuu that she'll be able to make friends in the real world and gives her thanks to Mato before disappearing into the wind. Afterwards, Yuu returns to her original body whilst Mato, having regained consciousness, reunites with Yomi. As life returns to normal, Mato, Yomi, Kagari and Yuu all become friends together whilst Strength returns to her place in the other world, alongside Black Rock Shooter. The episode ends with Black Rock Shooter saying she will continue fighting.