Duke Heros Archeon slays the black dragon Sellus, thus freeing the world from calamity—or so he thinks. But then, Sellus transmigrates into the body of Daphne Archeon, the duke’s cruel, petulant daughter, and somehow... this improves the girl’s personality?! Sellus takes over Daphne’s life and vows to train her body until she’s strong enough to kill her father. However, when dark mages threaten her family and kingdom, a feeling of righteous responsibility flares in her bratty little heart.

(Source: Tapas)