Dos huérfanos son abandonados en la puerta una iglesia, y tras quince años, ambos son unos apasionados jóvenes. Yuna es un mago con muchísimo talento que aspira a ser Rey Mago. Asta, por su parte, carece de aptitud mágica alguna y depende solo de su fuerza, pero tiene el mismo objetivo que su amigo: ser Rey Mago. Asta confía en que la entrega de su grimorio mágico despierte su magia, pero...

Con el ataque contenido, la capital recupera la paz poco a poco. El capitán Fuegoleon sigue inconsciente, pero el Rey Mago tiene algunas pistas sobre qué puede haber sucedido o qué busca el enemigo.

Todos se unen para acabar con el diablo, y es que si no es con un enorme esfuerzo conjunto, no hay ninguna posibilidad de vencer.

Una nueva batalla tiene fecha, así que el Rey Mago reúne a los capitanes de orden para informarlos de lo que sucede con el resto de reinos y de qué combatirán junto al Corazón para enfrentar a la Pica y al diablo.

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 Spade Kingdom successfully takes over the Diamond Kingdom and then sets their sights on the Clover Kingdom and Heart Kingdom. The Spade Kingdom troops get through the strong magic region using a mobile fortress which sucks up the mana of the Spade Kingdom citizens who were taken by force. But then Asta, who had finished his training with the Spirit Guardians, comes to the rescue! Meanwhile, Luck and Leopold head to the Spade Kingdom in order to try to take over one of their bases.

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.