Following the success in the Camelot Singularity, Ritsuka Fujimaru and Mash Kyrielight are assigned to the last Singularity in the Grand Order initiative. In Ancient Babylonia, 2500 BCE, they embark on a mission to secure humanity's survival. Upon arrival, they learn that three gods have threatened Uruk, the Babylonian city ruled by King Gilgamesh. Ritsuka and Mash must work together to fend off the invasion of mysterious beasts in Uruk under Gilgamesh's orders while investigating the true nature of the three gods' actions against humanity; but unknown to Ritsuka, an ancient entity is slowly rising from its slumber.