Armored Knight Iris(2007)

Armored Knight Iris is an anime series based on the adult game by Black Lilith. In a future where humanity shares space with multiple alien species under a federal government, ace pilots Iris and Mei Ling serve in the SSF's elite 101st unit. When Iris is captured during combat, she's transported to a brothel in the enemy-controlled city of Mirion and fitted with an explosive collar that detonates if she tries to escape. Trapped and forced into servitude, Iris must navigate her impossible situation while searching for a way to break free and reunite with her unit.