Maou desu. Onna Yuusha no Hahaoya to Saikon Shitanode, Onna Yuusha ga Giri no Musume ni Narimashita @comic

Galtor Luzen, resident Demon Lord on the continent of Masgenia, falls head over heels for the Hero's mother.
Once upon a time, a Demon Lord lost his wife and was all alone. But due to an unexpected turn of events, he met a woman he fell in love with at first sight. She happens to be...a Hero's mother?!
(Source: Comikey)