The Last Boss, the Church in Front of the Devil's Castle

A brief description of the manga The Last Boss, the Church in Front of the Devil’s Castle: After the Hero’s arrival, Sacred, the youngest priest of the church is sent to take care of an abandoned chapel right across the Demon King’s Castle, for it to serve as a resting place in his pursuit. Therefore, begins the connection between a priest and the Demon Lord. Was the person with the ideal ability sent to the chapel or will their experience bring forth chaos into the nation?