Finishing up the investigation at the Persian Gulf, Fujimaru and company are given a new order from the king. The new order is to retrieve a clay tablet that Gilgamesh had previously lost in the city of Kutha. Kutha was a city that suddenly disappeared after the emergence of the three goddesses, where every citizen had passed away. In such a quiet town, the entourage decides to split up in search of the tablet. Fujimaru suddenly wanders into a very frigid world. It is what people call "the underworld," a space separate from the physical world.

Fujimaru and entourage, in order to rescue the people left behind in the fortress city of Nippur after communications were severed, begin their battle against the fake Enkidu who had been awaiting them. With Fou's help, they were somehow managing to keep things even, but in the midst of battle, the Goddess of the Demonic Beasts finally appears. Even Merlin is at his wit's end facing her overwhelming power. Meanwhile, Ushiwakamaru and Leonidas I engage in a spectacular battle, standing up defiant against the Goddess of the Demonic Beasts. In order to break through the situation where it is hard to deliver a wounding blow, the two Servants unleash their Noble Phantasms with desperate resolve.