Asta and Noelle are captured along with Nero and they head toward the strong magic region near the border when Captain Yami and Magna arrive. Captain Fuegoleon and Captain Nozel also show up, causing the Devil Believers to panic. The captains try to talk to the Devil Believers, but their distrust for them is just too strong. The Devil Believers try to bring their powers together in order to face the Magic Knight captains.

The War against the Spade Kingdom begins in earnest as the Heart Kingdom and Black Bulls come under attack by Dante and Vanica of the Dark Triad.

Due to Nacht's spell, the Devil who has been granting Asta power since the beginning has appeared physically. To master his Devil powers, Asta must battle and defeat his Devil, and force him to submit. But Asta has other plans... Meanwhile, Yuno, Noelle, and the others grow stronger in order to take their revenge against the Dark Triad.