In the battle against the demon who attacked the academy, Lisalinde briefly regains her powers and memories as a succubus, only to quickly revert to her prim and proper personality. To ensure she can reliably activate the powers hidden within her, Lisalinde—still unaware of her true identity—is made to train alongside the hero’s party. One day, however, a large spatial distortion emerges on the outskirts of Academy Town, from which emerges an emissary of the demon lord, who challenges the hero to a duel. Accepting the challenge, Cain leads his party into the stronghold of humanity’s enemy: the demon lord!