Summoned by the powerful Shinju-sama, three young girls are chosen to become heroes to combat the menacing Vertexes, a threat to their world's peace. Initially unprepared for battle, Sumi Washio, Sonoko Nogi, and Gin Minowa struggle in their first encounter as magical defenders. Determined, they emerge victorious but acknowledge the need to enhance their teamwork and skills. However, as greater challenges arise, pushing the limits of their magical abilities, the girls face the dilemma of sacrificing part of themselves for humanity's safety. Will their victories demand too high a cost, questioning the true worth of their sacrifices for the greater good?