Maou desu. Onna Yuusha no Hahaoya to Saikon shita node, Onna Yuusha ga Giri no Musume ni Narimashita.

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)