In spring, two girls meet: Mato and Yomi. They each sense something in the other that they lack in themselves, and are drawn to each other in spite of their contrasting personalities. Though initially hesitant, they form a strong connection. But they both have secrets - and in an empty world, two girls fight: Black Rock Shooter and Deadmaster. A strange being, Black Gold Saw, watches their mysterious battle, laughing. This is the story of two girls, in two worlds, entangled by the threads of fate.