Kaiju Girls Black is set in Soshigaya-okura, a small town that's not as noisy as the city nor as quiet as the suburbs. In this prosaic setting, an ordinary high school girl named Satsuki Hiraga longs to join the heroic Kaiju Girls organization GIRLS. One day, she awakens to mysterious powers, but Satsuki instead finds herself recruited by Commander Black of the villainous organization, "BLACK STARS". What's a Kaiju Girl to do?