Saving the world once is not enough. Save it twice. Start off the game as the confused hero. Meet the charming ladies and woo them in between the battles.
The game becomes even naughtier with the night time conversation scenarios. Your every action in the ladies' rooms affect not only their love gauges, but their Blue Mage powers as well. And after you have made up your mind on which girl to wed, at the end of the the first generation adventures, there is the Honeymoon period. Enjoy.
The gender of your child and the mother of your child affects the second generation's abilities. So get closer to the mother to ensure that you give your child an extra leg up in his or her career as a hero(ine).