Kohei Morioka is a freelance photographer whose work for an occult magazine brings him into contact with the supernatural world he is normally oblivious to. A childhood accident involving paranormal forces left him unable to perceive spirits, a condition that paradoxically suits his career. This background also defines his unique status as an Ama Lamia, a Vampire Lover. No vampire can force him into servitude through a blood bond, and any vampire who drinks his blood will have their own infernal bonds of control broken, making him a significant anomaly in vampire society. Later in the narrative, it is revealed that his family sealed his own powerful latent spiritual abilities to allow him a normal life.

His personality is generally easygoing and he often displays a self-deprecating sense of humor. He is stubborn and fiercely resistant to being ordered around, immediately rejecting the idea of becoming a servant or slave. Despite this, he is fundamentally kind and cannot ignore someone in danger, which compels him to act. The core of his role in the story is his evolving relationship with the vampire Hazuki. What begins as a combative and involuntary arrangement slowly develops into a deep, protective, and romantic bond. He transitions from an unwilling participant who was dragged into her conflict to a determined guardian who risks everything to protect her from the vampire forces hunting her. His cousin, Seiji Midou, a powerful exorcist, becomes a crucial ally in his efforts to defend Hazuki. Kohei Morioka’s development is defined by his choice to actively fight a dangerous supernatural society and fully embrace his role as Hazuki’s protector rather than remain a passive human caught in their world.