Mahou Shoujo Isuka

Based on the erotic game by Black Lilith. The evil stone conceives a part of the king of the hell's power in a different world. To prevent his revival, the stone is implanted into a body of a magical girl! Now the clans from the hell follow after her. The evil stone cannot be regained by a simple destruction of the body. Thus, they start disgracing the magical girl in various ways! (Source: DLsite English)