Makai Senki Disgaea 3: Return [The Best]

The story takes place in the Evil Academy where Lord Mao, the Academy's Top Honor Student (because he has never been to class), has decided that he needs to gain "the Power of the Hero" to get revenge on the Overlord, who also happens to be his father, from thousands of hours of research into comics, anime and video games. Along the way he meets Raspberyl who introduces herself as an old friend of Mao and the Academy's Number 1 Delinquent (as she does all her homework, has perfect attendance and volunteers in her spare time). Soon after, the pair meets Almaz who has come to protect the Princess from the Overlord. Mao, seeing Almaz's title as "Hero", kidnaps him while Beryl tries to rescue him. Eventually Mao gets away with Almaz as class starts and Beryl cannot be late. Mao then takes Almaz into his heart where they can switch titles thus giving Mao the power he needs to defeat the Overlord (he then comments how economical the game is as the final boss will be defeated in the first chapter). Mao and his slaves, including Almaz who is now a "Demon-in-training", then go face the Overlord who is much bigger than they expect. The fight actually occurs without the Overlord's knowledge on the palm of his own hand and the party is thus defeated.