Twelve-year-old Touta Konoe has lived his entire life in a rural town. He dreams of visiting the capital one day, where a tower reaches into space. To achieve this dream, he is tasked with defeating his teacher and caretaker, Yukihime, who will then allow him to go to the capital. Touta's life is turned upside down when a bounty hunter arrives to claim the prize on Yukihime's head. In a desperate attempt to save both his mentor and friends, Touta follows Yukihime's instruction to drink her blood, turning him into an immortal monster capable of defeating the bounty hunter. Yukihime reveals herself to be Evangeline Athanasia Katherine McDowell, a centuries-old vampire. With her identity now exposed, she and Touta flee to the capital and embark on an exciting adventure that will change both of their lives forever.