Ep 0: Initium IterIn the past, Romani "Roman" Archaman joins Chaldea and acts as the primary doctor for Mash Kyrielight, a designer baby who was turned into a Demi-Servant, a Heroic Spirit put inside the physical body of a human. While the experiment is successful, the Heroic Spirit goes berserk and attempts to attack Chaldea before being suppressed by Mash. Afterwards, the Heroic Spirit refuses to assist Chaldea, though that doesn't affect their plans to use Mash as a catalyst to summon more Servants. Roman is concerned about Mash's limited lifespan and befriends her, teaching her about humanity and the outside world, and she comes to wish to see a clear sky. In 2016, Mash meets Ritsuka Fujimaru, beginning their journey to save the world by traveling back in time to resolve numerous Singularities and meeting many people and historical figures in the process. Eventually, Mash and Ritsuka prepare to enter the Seventh Singularity.
Ep 1: Absolute Demonic Front BabyloniaRitsuka and Mash Rayshift to the Seventh Singularity, which is the ancient city of Uruk in the year 2600 B.C. However, they end up landing far from Uruk due to the city being protected by a bounded field. They fight off numerous demonic beasts and are briefly assisted by a mysterious and powerful woman before she takes her leave. Enkidu then arrives to assist Ritsuka and Mash and guide them to Uruk. Enkidu reveals he already knows their mission to fix history by recovering the Seventh Holy Grail from the singularity, and explains that Mesopotamia is on the brink of extinction due to the Three Goddess Alliance, who seek to destroy humanity. He then shows them a massive wall humanity has built to protect what is left of human civilization: the Absolute Demonic Front Babylonia. Meanwhile, a pair of cloaked figures take note of Ritsuka's arrival.
Ep 2: Fortress City Uruk
As Enkidu leads Ritsuka and Mash to Uruk, they encounter the cloaked strangers, who point out that since Gilgamesh had only recently returned from his quest to try and revive Enkidu, this means that Enkidu should already be dead, outing the current Enkidu as an impostor working for the Mage King. His cover blown, Enkidu attempts to attack Ritsuka and Mash but they are spirited away to safety by the mysterious pair. The strangers introduce themselves as Merlin and Ana, both Servants summoned to the Singularity to fight for Uruk and assist Chaldea. It is also revealed that Fou is familiar with and intensely dislikes Merlin. Merlin guides Ritsuka and Mash to Uruk to meet the king, Gilgamesh. In order to test Ritsuka and Mash, Gilgamesh challenges them to a battle.
Ep 3: The King And His People
Mash and Ana are forced to battle Gilgamesh, but he is unimpressed. He reveals that he already possesses the Holy Grail, which is why the Three Goddess Alliance has declared war on Uruk. However, he refuses to hand over the Grail to Ritsuka, stating that it is his treasure now. Suddenly, the woman Ritsuka met before barges into the throne room, revealed to be Ishtar, one of the members of the Three Goddess Alliance. Ishtar briefly skirmishes with Gilgamesh, Mash, and Ana, but withdraws after noticing something odd about Ana. Gilgamesh allows Ritsuka and Mash to stay in Uruk, assigning his advisor Siduri to look after them and giving them an opportunity to work to earn his favor. They are then met by the other servants Gilgamesh had summoned: Ushiwakamaru, Benkei, and Leonidas. Ritsuka and Mash are then assigned to perform numerous mundane tasks. They are eventually given a day off, where they help Ana destroy evil spirits lurking beneath the city. Meanwhile, Enkidu assures his mother that she will be the Goddess to destroy Uruk and seize the Grail.
Ep 4: Call of the Jungle
After one month of performing menial tasks, Ritsuka and Mash are assigned by Gilgamesh to investigate the neighboring city of Ur. They travel there with Merlin and Ana, where both Ritsuka and Merlin suspect the Grail in Gilgamesh's possession is not the cause of the Seventh Singularity. They then have a brief and confusing encounter with a woman calling herself "Jaguarman" before she disappears. Upon arriving at Ur, the residents claim they are in no danger and do not require Gilgamesh's protection. Merlin deduces that the people of Ur had made a deal with a god for protection in return for daily sacrifices, observing the absence of men among the population. The residents confirm his theory, pointing out they have no way of opposing a god. Jaguarman then attacks, revealing she hasn't killed the sacrificed men, only put them into forced labor for her own purposes. Mash and Ana attempt to fight back, but are outmatched. Ritsuka is forced to call a retreat back to Uruk, and promises to return to save Ur. The next day, Gilgamesh meets them at their headquarters.