Mahou Shoujo Isuka(2010)

Mahou Shoujo Isuka is an adult anime series based on the visual novel by Black Lilith. A magical girl is implanted with an evil stone containing a fragment of a hell king's power, meant to prevent his resurrection. When demon clans pursue her to reclaim the stone, they subject her to relentless degradation and torment. The stone cannot be destroyed by simply killing its host, forcing the girl into an escalating nightmare as her pursuers employ increasingly brutal methods. Dark and explicit, the series explores the consequences of bearing such a dangerous burden in a hostile supernatural world.