Mourning Sun - The Celestial Shadow Series, #1

He is the shadow of a century-old crime. She is the light that will burn him.
Seventeen-year-old Mairin Cote has spent her life trying to be invisible, dodging the cruelty of Highland Home's elite and hiding the terrifying premonitions that haunt her sleep. But invisibility becomes impossible when the boy from her darkest nightmare walks into her first-period English class.
Mathias Auer is beautiful, wealthy, and dangerously polite. He is also a Soul-Drifter—an immortal cursed by a Blood Vow to mourn the girl he murdered in 1920.
Mathias didn't come to Highland Home for a fresh start. He came for Mairin. Drawn by her unique psychic beacon, he believes she is the Mourning Sun—the only one capable of helping him find Kathryn, the lost love he turned into a monster and abandoned a century ago.
But helping Mathias means unearthing a secret that will shatter Mairin's world. Her family aren't just shopkeepers selling crystals; they are Sentinels, ancient guardians hiding the very woman Mathias seeks. As the ruthlessly efficient Serpent Keepers close in to destroy them all, Mairin must choose: protect her family's lies, or trust the monster who promised to love her, even as he hunts for another woman.
The sun is rising on a history of blood. And Mairin is the only one who can see the end.