Writer Mitsuru Hasegawa and Annaka Yuusei (a.k.a. Anna), who runs a real estate business, are childhood friends and lovers. They have a secret: Anna is a "biter" who feeds on human blood, and Mitsuru is a "nectar" whose blood the "biter" likes. The two signed a "symbiotic contract" in which they could not live without each other's blood. Anna, who...