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

Meet Galt Luzen, the Demon Lord. Well, the Demon Lord of his own continent, anyway. After his wife passed away, he gradually withdrew from his social life and started to do more of whatever Demon Lords do. Enter Angelica, the Hero. Heroine. Whatever. She's a paladin of goodness, who wants nothing more than to defeat the Demon Lord. However, she is no match for him and is utterly defeated. As Galt is not a completely evil Demon Lord, he takes Angelica, still unconscious, as well as the other members of her party, back to their families so they can rest their wounds. As he is bringing back Angelica to her home, however, he meets her mother, Reitia, who is the splitting image of his former wife. As they bond over tea, Galt's feelings get the better of him, and he proposes to Reitia on the spot. Surprisingly, she accepts. How will Angelica cope with a literal demon for a stepfather? Can Galt take care of someone who has taken a blood oath to kill him? Just what are Demon Lords in this world, anyway, for them to nonchalantly treat the battles of good and evil as if they were sports? Read and find out.