Taito wakes up one day and realizes the vampire whispering in his dreams actually saved his life, and now she's real, and now he's stuck in her world whether he likes it or not. The show treats its romantic setup like a genuine trap instead of a wish-fulfillment fantasy. What looks like a harem comedy about a guy getting attention from supernatural girls is actually about someone learning to want the person who chose him first, even when everything else is screaming louder.

Taito keeps slipping into vivid dreams about a mysterious female vampire who claims she has given him her poison. Sometimes he even seems to hear her voice while awake. Kurogane Taito is a first-year high schooler who has stopped believing that effort pays off and simply lets the days drift by. Then he walks away from an accident that should have killed him, and his world turns upside down. As buried memories resurface, he recalls a pact he made nine years ago with Saito Himea, an elder vampire, along with a curse. He also remembers the girl herself, who was taken and has been held captive ever since, waiting for him to set her free. Adapted from Kagami Takaya's light novels, the show blends supernatural drama with comedy, romance and ecchi elements.