In 1920s America, Rosette Christopher hunts demons for the Order of Magdalene alongside her partner Chrono, a demon who fights at her side under a contract that quietly spends her own lifespan. The two work their way across the country while Rosette searches for her younger brother Joshua, carried off by the demon Aion. A small crew gathers around them along the way, including the apostle Azmaria Hendric, in this manga by Daisuke Moriyama.