In Tsukimori City, a unique heroine named Mia leads a double life. By day, she's a typical high school student, but when the villainous Calamity Co. Leviathan threatens the city, she transforms into a fearless hero, Gaimoon. Little does she know, her childhood friend Takeru, seemingly ordinary, harbors a dark secret as the leader of Calamity Co. Leviathan, Lord Helvenom. As fate entwines their paths, Takeru must confront his conflicting loyalties between his friendship with Mia and his duty to face her as her sworn enemy. A gripping tale unfolds as the battle of good and evil tests the bonds of love and loyalty in this compelling hero novel set in Tsukimori City.