The year is 2016, and glitches found in humanity’s past threaten the sustainability of its future. The Chaldea Security Organization—tasked with preserving human history for as long and as strongly as possible—has developed a new method of time travel to repair these events, stabilizing humanity’s future. But when an unknown threat pushes mankind to the brink of extinction, young recruits Mash Kyrielight and Ritsuka Fujimaru find themselves at the helm of the rescue mission: Obtain the Holy Grail in a face off against fate itself…

Legends tell of a race of divine beings known as Seraphim, whose unseen influence is felt throughout the world. Those with the ability to commune with the Seraphim became known as “Shepherds”, the most pure-hearted of which could even be granted a Seraphim’s power. While some would praise these empowered Shepherds as living paragons, others would fear their strength and call them demons. Sorey is a young human who has spent his entire life in The Divine Forest, a holy place where he lives in harmony with many Seraphim. Enraptured by the legends within an ancient tome, he makes daily excursions into a nearby ruin in the hope of learning more about the Seraphim and their history, along with his Seraphim childhood friend Mikleo. One day, he is trapped by a cave-in alongside his friend and a young knight named Alisha, who is investigating a series of natural disasters that have been plaguing the world. When Sorey discovers that the Seraphim may be involved, he resolves to leave his home alongside Alisha and find the truth.