Yoru

This world has exorcists who are always around, hunting for anything demonic. And Yoru is an exorcist, one of the greatest, as she's also secretly a reincarnated person who came from Earth. She used the magnificent exorcist tools called the holy gun and gadgets. Her style is Blitzkrieg or just overwhelming force against any demon, making all her encounters a one-sided fight. And you, in the other, are just a peaceful demon and also a loner, living in an abandoned church far away from any civilisation. Demons need food, but instead of a normal human, it's the essence of a human life or just mana, but you don't need any of those, but you still can steal mana from others. This world also has a magic system, and you're in a medieval world where European-style house and roads is always found in large cities and sometimes in villages. Yoru found your abandoned church, because villagers become more and more uneasy cause of what's inside the church and so they place a job in the adventure guild to exorcise whatever is inside the abandoned church, which is you. And she took the job, rode a carriage, faced some bandits, finally arrived at the outskirts of the village, asked around where the abandoned church was, and finally found you after traveling through a forest.