Renowned adventurer Adol Christin and his companion Dogi arrive in Balduk, a city annexed by the Romun Empire. But at the entrance to the city the main character is detained. While in prison, he meets a mysterious woman named Aprilis, who turns him into a monster, a being with supernatural powers and the ability to banish evil beings. Now Adol must team up with his comrade to fend off the deadly threat emanating from the dark dimension called Grimwald Nox, while also unraveling the secrets of Monstrum's curse and the truth behind the unrest within Balduk.