Fujimaru successfully retrieves Gilgamesh's clay tablet, and within a deep slumber, he remembers his encounter with the King of Mages in London, the Fourth Singularity, which renews his understanding of the importance of the final Holy Grail. Meanwhile, Merlin suspects that the Demonic Beasts at the Northern Wall are planning a large-scale attack, and takes Fujimaru and company to the Northern Wall. There, they see a squad commanded by Leonidas I putting up a struggle. Once there, Fujimaru and company hear from Ushiwakamaru that communication with the fortress city of Nippur to the north has been severed, and they head out towards Nippur.
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.
