When the sky turns red, the moon turns black, and monsters begin roaming the streets, Satsuki Kakeru is at a loss for what to do. Along with his best friend Yuka, they try to decipher why they have been sent to this strange world, which is seemingly empty aside from themselves. However, when the Red Night ends, Kakeru and Yuka believe it was all a dream—until it happens again, and they are left in a dangerous situation. They meet four others in the same predicament: Kusakabe Misuzu, an expert swordswoman; Tachibana Kukuri, a strange mute girl who looks uncannily like Kakeru's deceased sister; Hirohara Yukiko, a lively young girl whose personality reverts to that of a cold killer when her glasses are removed; and Tajima Takahisa, a young pyrokineticist. As the six of them band together to survive and discover what this mysterious world is, things take a turn for the worse as six shadows appear before them...

In Fuyuki City, the Fifth Holy Grail War is about to commence a lengthy battle of blood, death, and misery. High school student Rin Toosaka has trained her entire life for this moment—to become a magus capable of being a Master in the war. Summoning her Servant known as Archer, Rin finally sets foot into the battle. Discovering that one of her acquaintances, Shirou Emiya, is drawn into the war as well, Rin offers to form an alliance for the time being. And as the two of them grow closer, Rin begins to learn more about Shirou's fate and ideals. Nevertheless, her goal remains the same: to win the all-powerful relic that can fulfill the wishes of those who are victorious after the war—the Holy Grail.

Although citizens of London view dragons as a fairy-tale myth, statistics confirm that 72% of the city's deaths are caused by these grotesque beings. Unable to see them, the public is oblivious to their existence. However, in a mirror dimension to Front London, exists a place where dragons can be seen with the naked eye—Reverse London. Ninny Spangcole is a member of a popular girl group. But in Reverse London, she works as a Witch at Wing Bind—an organization that dispatches agents to exterminate the beasts and protect the citizens of both Londons using magic. Ninny and her partner, Noel Niihashi, in addition to their jobs, safeguard Baldo Ywain Parks, a young man with an odd connection to the dragons. Thanks to the Wing Bind's hard work, there were no fatal dragon attacks for almost a century. But the peace shatters when Baldo's presence unexpectedly causes a Dark Dragon to wreak havoc in the city. The witches are further inconvenienced when Ninny's troublesome former bandmate appears in Reverse London—in tandem with another powerful dragon.

In a world inhabited by demons, cyclopes, and other fantastic creatures, humans stand apart as the outcasts. Quick to anger, the human race engaged in a war that all but wiped them out. The few humans that remain are seen as a delicacy, serving no purpose but to be hunted down and eaten. One day, a golem—a wandering protector of nature—encounters a lone human child while patrolling. Inspired by her enthusiasm, he takes the girl, named Somali, under his wing. Together, the duo embarks on a journey to find Somali's parents and bring her home.