Disgaea 2: Cursed Memories

Fifteen years ago, a powerful Overlord by the name of Zenon appeared on Veldime and cursed its human population. Since then, all its inhabitants became demons and were to remain that way if the curse was not broken.

However, a young man named Adell was the only human unaffected by the curse. Wanting to save his family and return them back to their true form, Adell decides to defeat Zenon. Adell's mother, a summoner, tries to summon Zenon and failed, and instead summoned Rozalin, Zenon's daughter. They later on go on a quest to go find Zenon and return Rozalin to him, and then defeating him so that the curse would be lifted, and then so his family would be human again.