I'm a Demon Lord. My Second Marriage was with the Hero's Mother, and the Hero Became my Step-Daughter.

Demon Lord Galtau Leuzen was attacked at the Demon Lord’s Castle by the hero’s party, but quickly turned the tables on them. After they were all knocked out, the kind-hearted demon lord returned them all to their families, which was when he had a fateful encounter: He instantly fell for the hero’s mother, Laetia, a widow who was raising her hero daughter alone. Galtau, who also lost his wife and lived in loneliness ever since, felt drawn to the hero’s mother. After somehow easily getting the OK, he married Laetia, but naturally the hero couldn’t accept the demon lord suddenly becoming her father, leading to a weird household situation. In order to get along with his new step-daughter, the demon lord now has to put his all into creating a new home for his family.