After death, those who have committed sins that are deemed unforgivable are known as Sinners and are marked with thorns. To prevent Sinners from being sent to Hell, Sin Eaters take on their sins and punishment. Rukiko, a village girl, feels a strong desire to protect Raika, a valuable treasure and the Fire of God for her village, from Gaii, a Sin Eater who aims to cleanse his own sins. Upon learning about Gaii's past, Rukiko's feelings toward him shift. Despite Angel Musa, the servant of God who guided her mother to Heaven, advising her not to sympathize with Gaii, Rukiko is left conflicted about whom to trust.
