Sooha has spent her entire life hiding her superhuman abilities, forced to suppress her true nature to avoid being mistaken for a vampire. Already wrongfully accused and blamed for the death of her childhood friend, she enrolls at Decelis Academy, an unusual night school that is said to be an impenetrable sanctuary where supernatural beings cannot enter.

The seven most popular boys at Decelis Academy are vampires. Heli, Jaan, Jino, Shion, Jakah, Noa, and Solon share this secret, keeping their identities concealed while navigating the intense rivalry with the werewolf pack from the prestigious nearby school, Riverfield. Despite the dangers, Heli befriends Sooha after discovering her secret and introduces her to his close-knit circle. Though the boys vow to protect her, they find themselves caught in an inexplicable and powerful attraction to her, each feeling an uncanny willingness to follow her wishes.

Tensions erupt when a series of horrific murders plague the city, with vampires immediately suspected as the culprits. The vampire boy and the werewolf pack blame one another, existing in a state of constant vigilance. However, as Sooha becomes entangled in the investigation, she realizes that the conflict is far from simple. The mysterious events are rooted in a centuries-old enmity between the two races, and the boys from Decelis Academy are discovering that their connection to Sooha is not a coincidence, but a bond forged by fate and a shared past life.

The narrative arc follows the group as they confront a villain named Dardan, whose schemes threaten to tear apart the fragile balance. When Dardan injures the vampire brothers and abducts a member of the werewolf pack to complete a dark ritual, the race against time begins. As the full moon rises, the boys must navigate to the Blood Altar to save Sooha, leading to a confrontation that forces them to confront the truths of their past lives where they once served as knights sworn to protect a single person. The story explores the boys growth as they move beyond their ancestral prejudices, learning that true strength lies in protecting one another, while Sooha grapples with her hatred for the very monsters she is growing to trust.

Dark Moon: The Blood Altar is the main installment of a broader narrative universe that includes prequels detailing the orphans origins at Vamfield House and the history of the werewolf kingdom of Vargr, as well as a spin-off focusing on the werewolf pack in The Grey City.