Ritsuka Tachibana has always been a model student, so she is utterly stunned when the student council suddenly summons her for violating school regulations. Under the leadership of Rem Kaginuki, the council—which also includes Urie Sogami, Shiki Natsumezaka, and Mage Nanashiro—attempts to interrogate her, but it quickly becomes apparent that they have hidden agendas. Yet, this is merely the start of Ritsuka’s troubles. When her mother is kidnapped, her world is turned upside down, and Ritsuka is pulled into a power struggle between vampires and devils. Both factions are hunting for the "Grimoire," a forbidden artifact that grants its owner dominion over the world, and Ritsuka is somehow linked to this mysterious object. The return of Ritsuka’s protective brother, Lindo, from abroad offers her hope that life might return to normal. However, even her sibling is keeping his own dark secrets. Ritsuka starts to wonder who she can truly trust, and whether she can ignore her growing attraction to the devilishly handsome members of the student council.