On the verge of extinction, humanity has shrunk in size and now lives exclusively in the city-state of Flandore, within cities protected by glass domes. Outside these domes, vicious lycanthropes thrive in the darkness; inside, a strict divide exists between nobles and commoners. Noble blood allows its bearers to wield mana, granting abilities that surpass human limits and greatly aid in defeating lycanthropes. Melida Angel, a noble who is already 13 years old, has yet to manifest her mana and attends an elite academy where she is mistreated for this deficiency. To assist her, Kufa Vampir is ordered by the Angel family to serve as Melida's tutor. Although Kufa appears to be a simple mentor, a hidden motive drives his assignment: he is to assassinate her if he confirms she lacks mana. Kufa's investigation eventually leads him to conclude that he must eliminate Melida. However, witnessing her unwavering determination, spirit, and self-belief in combat strikes him, and he chooses instead to offer a path for her to manifest her magic. As Melida learns to use mana through Kufa's teachings, he abandons his mission and risks everything to keep his discovery of Melida secret from the Angel family and his own guild. Yet, both Kufa and Melida will soon realize that concealing their secret is not their only challenge, as unforeseen trouble awaits just around the corner.