In a world where magic once thrived but was later sealed by the sacrifice of seven powerful mages, the stage is now set for the Granbelm battles within the magic seal Magiaconatus. High school student Mangetsu Kohinata finds herself thrust into this mystical realm on a full moon night, mistaken for an enemy mage. Saved by the skilled Shingetsu Ernesta Fukami and her Armanox Viola Katze, Mangetsu is granted the power of the Armanox White Lily by Magiaconatus. With newfound abilities, she joins forces with Shingetsu to partake in Granbelm and fulfill her friend's deepest desire, unraveling a world of magic and mystery.