Yami and Vangeance are taken to the Spade Kingdom so that the ritual to open the  gate to the underworld can begin. Despite how hurt he is, Asta tries to escape the imfirmary to go and save Yami, however he is stopped by a mage named Nacht Faust, who also happens to be a devil-possessed.

After his inner devil is summoned in a ritual, Asta must win the battle against him if he hopes to regain his power.