Maou to Odore!: Legend of the Lord of Lords

A man awakens in a room to find an unfamiliar woman present. She claims he is the reborn ruler she once served, a Demon Lord sealed by the land's goddess long ago. Her attempt to restore his memories fails, causing her distress. To help him regain his past, she resolves to take him to locations where fragments of his sealed power are said to reside. Under her insistence, he accompanies her. In their first destination, a dungeon, he rescues a priestess who believes he is the Messiah destined to deliver the land from darkness.