Ritsuka Tachibana has always been a good student, so she is completely shocked when she is suddenly summoned by the student council for breaking school rules. Led by Rem Kaginuki, the student council—also consisting of Urie Sogami, Shiki Natsumezaka, and Mage Nanashiro—tries to interrogate her, but it soon becomes clear that they have ulterior motives. However, this is only the beginning of Ritsuka's misfortune. When her mother gets kidnapped, her life is turned upside down, and Ritsuka gets drawn into a battle for supremacy between vampires and devils. Both groups are searching for the 'Grimoire,' a forbidden item that allows its owner to rule the world, and Ritsuka is somehow connected to this strange artifact. The return of Ritsuka's protective brother Lindo from overseas gives her hope that life could return to normal. But even her sibling is harboring his own dark secrets. Ritsuka begins to question whom she can trust, and if she can ignore her growing attraction toward the devilishly handsome student council members.