A Story about Getting Picked up by the Former Demon King

From DLsite: One day, a former noble lady with nowhere to go meets a strange man who picks her up. Kanon, the daughter of an aristocrat, was kidnapped by bandits for money, but her family abandoned her and so they decided to sell her instead. Under those circumstances, she gets rescued from the bandits one day by a demon, the former demon king who will take her with him. In the short span of time that she was rescued, Kanon suddenly got demon markings on her supposedly ordinary human body. This R18 release was remade by Kodansha's Palcy as a Shoujo manga.