Fate/Grand Order: Zettai Majuu Sensen Babylonia

Synopsis

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.

(Source: Wikipedia)