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 had a crush on Mitsuru since he was young, was as happy as having his dream come true. However, at the same time, Anna also felt guilty for what he did to Mitsuru... (Source: ihr HertZ, translated) Note: Includes bonus epilogue chapter.