The story takes place in the distant future, after Earth has been ravaged by an event called Armageddon. Humans are at war with vampires, and to protect themselves from the vampires, the Vatican has called in allies. Abel Nightroad, a seemingly defenseless man, travels the country as a representative of the Vatican. He is also part of "Ax", a special operations group led by Catherina. During a battle, Abel meets a young girl named Esther, an encounter that will change much about the future of the war...