Valkyries—legendary female warriors from the land of gods, Asgard—are sent by Odin to protect Earth against the growing threat of demons. To overcome these threats, nine valkyries under the guise of the Saotome sisters will have to level up by performing a variety of romantic acts with their official lover, Einherjar. Meanwhile, the socially anxious Takuma Akutsu learns that Odin has chosen him as the valkyries' lover. Despite his utter horror, however, he agrees to let the sisters stay in his big yet empty house to help them in their war against demons. With nine beautiful women sharing his roof, will Takuma manage to prevail over his fear of society and become someone worthy of saving the world?

The story revolves around D, the infamous dhampir (born of a vampire father and a human mother) outcast and renowned vampire hunter. His prowess at hunting the creatures of the night allowing his acceptance among humans, he is called upon to locate Charlotte Elbourne, the lovely daughter of an affluent family who has been mysteriously kidnapped. When the sun sets, the hunt goes on! Charlotte's father offers a rich bounty, be she dead or alive, a task D willingly accepts, even with notorious Markus brothers and their gang of bounty hunters seeking the prize as well. Amidst the chase and unknown to all lurks, a sinister evil which has been secretly manipulating their every move and has set a chilling trap that none will expect and few will survive. With the tables turned and the secrets revealed, the hunters could quickly become the hunted! (Source: AniDB)

The cheerful Yuuki Cross and the gruff Zero Kiryuu are members of the disciplinary committee at Cross Academy, which houses two very distinct classes: the Day Class and the Night Class. Their job consists of upholding order between the classes when they switch out. While that may not seem like an especially difficult task, the Day Class is unaware of the truth behind the Night Class—their utterly gorgeous students are vampires. Ten years ago, Yuuki was saved from a vampire attack by Kaname Kuran, a Pureblood vampire. Now, Kaname is the leader of the Night Class, and Yuuki's disciplinary committee position allows her to see him again, making her feelings for him grow complicated. Meanwhile, Zero bears a white-hot hatred of all vampires and believes they can never live in harmony with humans. But a secret from Zero's past soon threatens the fragile peace of all at the academy, and things may never be the same again.

When the missing Zero Kiryuu returns to Cross Academy, Yuuki Cross is relieved to see him safe, but finds that Zero has changed in more ways than one. As a result of choices he made, Zero is plagued by visions, and he seeks to uncover the reason behind them—unaware that the answers may be much closer than he thinks. Soon Yuuki also begins to be tormented by ghastly hallucinations, and she seeks an explanation about her shrouded past from the only one who can provide clarity: Pureblood vampire Kaname Kuran, who is closest to her heart. But what will happen when the truth is finally revealed?