Shiro Seijo to Kuro Bokushi takes place in a small church atop a hill, where Pastor Lawrence cares for Saint Cecilia, a young holy woman whose presence is a beacon of hope for the villagers. To the people who visit the church, Cecilia appears elegant and dignified, and her mysterious powers protect them from the weakness of their minds and from outside evils. Once the villagers have gone home, however, the saint drops her formal composure and reveals the lazy side that only Lawrence ever sees. Even though Cecilia stands as the guardian of the people, Lawrence remains determined to shield her from harm in return.
What Lawrence does not realize is that Cecilia is deeply in love with him. She joins him on his shopping trips, watches over his daily life, and offers him divine protection every day, while he stays oblivious to what her feelings really mean. Cecilia, meanwhile, keeps expressing her affection in ways that seem obvious to everyone but him. As they continue sharing the quiet routines of church life and caring for others together, the bond between saint and pastor grows stronger.