Oichiitte Yutte yo.

The story centres around Kagami Ibara, the young lady of the influential Kagami Financial Conglomerate and a hopeless tsundere who pushes everyone away with her twisted personality.
One day the vampire Delacroix appears before her and declares that he'll help her get closer to her crush in order to improve the taste of her horrid blood.
What's going to come of their cooperation?