七彩のラミュ Lamuros de Sept: The Seven Colors of Lamuros

From the introduction:

Nearly a year ago, the demon king was slain by the human army, led by the hero Gilbert. Since then, the people managed a turnabout, making demons and beasts the hunted instead of the hunters. This seemed to be leading humanity to a new era of peace. However, the daughter of the demon lord, Lapis, is still around and has designed a plan to make demon-kind flourish once again. With the aid of powerful (and sexually inclined) demons, she shall make the seven princesses of light fall into their ranks and use them to plunge the world into darkness.