The Demon King's Warrior Daughter

Nobody said being a parent was easy. It's especially hard for Belphegor Verscios, the adoptive father of an exceptionally gifted human girl who insists on becoming a warrior someday and defeating the Demon King—who, unbeknownst to her, happens to be him. But when you're a doting father like Belphegor, what else can you do but try to support her dreams while simultaneously making sure she never reaches her goal? It's a fine line to walk, but he must succeed at any cost, or suffer the worst fate he could ever imagine... disappointing his daughter.

(Source: Webtoon Entertainment)