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.

On the surface, Ryousuke Kaga is the token perverted teenager, spending his days ogling women and indulging in erotic reveries. Because of this, Ryousuke is ostracized by his classmates. Only his childhood friend Mina Okura knows that behind his lecherous persona lies a compassionate boy who has sworn to be chivalrous to girls, believing they are treasures that must be protected. One fateful day, Ryousuke runs into Lisara Restall, a Soul Reaper hailing from a noble family, whose primary objective in the human realm is to locate a magically potent person known as the One. In order to fuel her movement with magic, she decides to form a provisional contract with Ryousuke: to use his sexual desires as a source of energy. Carrying out this peculiar arrangement with Lisara, Ryousuke encounters many disparate individuals but also learns of the intriguing yet dark secrets surrounding his world.

Inako is a minor country, enclosed by two superior countries: the militaristic Milidonia, with its goal of conquering as much land as possible, and the monotheiestic Selenfalen, devoted to the deity Saint Philia. Ani Inako is the sole princess of her country, and in order to eliminate hostility between the three countries, she is sent as Inako's representative to a peace treaty signing in Selenfalen. However, Ani's hopes of a smooth ceremony are shattered when she meets the eccentric princes from her rival countries. With the treaty binding the three countries together, Ani and the princes must learn to overcome their differences. Together, they search for common ground on which to develop their friendship.

Uruno, a useless wolf, is on the road searching for a new place to call home. He soon comes upon a whole forest full of useless animals—that is, animals that don't live up to their species' usual character. After a short fight with the smoking, bad-tempered rabbit, Usahara, Uruno decides that he wants to move on... but changes his mind upon meeting Chiiko, a clumsy cheetah girl. It's love at first sight for Uruno, and after deciding to stay for her, he continues to hope that even though he's a good-for-nothing, he'll win her over someday. That is, if living with the other strange residents of the forest—including the aforementioned smoking rabbit, a sake-drinking unicorn, a near-sighted eagle, an orca that cannot swim, and a shy pegasus—doesn't get to him first.