One day, a former noble lady with nowhere to go meets a strange man who picks her up. 4u45z

Kanon, the daughter of an aristocrat, got kidnapped by bandits for money, but her family abandons her and so they decide 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...

(Source: DLsite Girls Maniax)

Note: This is the original TL/R18 doujinshi that got serialized in Kodansha's Palcy magazine as the all-ages shoujo manga "Moto Maou-sama to Koisuru Hana - Kazoku ni Suterareta Ma no Ouzoku ni Metoraremashita" (元魔王様と恋する花〜家族に捨てられたら魔の王族に娶られました〜).