A man standing on a bridge, preparing to end his life, is suddenly confronted by a girl who looks like an ordinary high school student. She makes an unusual demand: Give me your blood, mister. The man, a hitman by trade, finds the request oddly convenient, deciding he would not mind dying at the hands of such a beautiful girl. The girl is a vampire, and when she moves to bite him, the man accepts his fate. However, rather than granting him death, this encounter sparks an unexpected bond between a human who has lost his will to live and a supernatural being who needs his blood to survive.

The series is set in a contemporary world where the uncanny exists alongside the mundane. The central pair consists of a teenage vampire girl, who appears indistinguishable from a normal student, and a professional hitman whose suicidal ideation masks a deeper detachment from life. The hitman, described as possessing a demeanor reminiscent of a stylish bounty hunter, steps in to protect the vampire from predatory loan sharks, shifting their dynamic from predator and prey to reluctant partners. The official description for the series frames it as a collection of tales where humans and the uncanny meet, focusing on lost halves finding their echo.

The narrative opens with the bridge encounter, which serves as the inciting incident for the story. Following this, the hitman offers not just his blood but himself to the girl, an act that leads to a strange cohabitation or partnership. As they navigate this relationship, they become entangled in conflicts with other dangerous elements of society, such as the loan sharks who threaten the vampire. The early chapters suggest a structure where the duo may team up to confront various antagonists, potentially including a larger vampire society or criminal underworld. The core of the story revolves around these two broken individuals finding a new purpose in each other, exploring themes of redemption and connection against a backdrop of supernatural action and suspense.