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!