In Dark Moon, Sooha has spent her life hiding her superhuman abilities so no one mistakes her for a vampire. After being accused of being one and blamed for her childhood friend's death, she enrolls in Decelis Academy, a night school where supernatural beings such as vampires and werewolves are said to be unable to enter.
There, Sooha meets Heli, who reaches out to her even after discovering her secret. Heli introduces her to Jaan, Jino, Shion, Jakah, Noa, and Solon, a tightly bonded group of boys who each possess different powers. Yet their attachment to Sooha feels deeper than simple friendship; they seem curiously drawn to her, as if they would do anything she asks.
When a recent murder is blamed on a vampire, the unsettling history behind Heli and his friends begins to surface. As they try to protect Sooha from the supernatural world, she is pulled into the centuries-old rivalry between vampires and werewolves, and the hatred that has followed her since childhood grows even harder to untangle. The closer Sooha gets to the truth, the more she realizes she may be nearer than ever to the creatures she has always feared.