Arata and the others appear in a world floating in a rift in the sea of parallel dimensions. Monsters attack. The legendary grimoire, "Fragments of the Iliad" challenges them to a fight. An evil power awakes in Arata due to his anger when the Astil Codex are sealed...

Lugh attacks the school while Arata and Mira are being held far away. Yui evacuates everyone in the school into her dream to protect them, and Levi sets out to fight alone. But Lugh is a demon lord candidate who has obtained a demon lord element.