Makai Kishi Ingrid

A 2009 Hentai anime set on the same universe as Taimanin Asagi, Makai Kishi Ingrid (which can be translated as "Hell Knight Ingrid") is a loose adaptation of the visual novel Taimanin Murasaki but focused on the supporting character Ingrid. It was released as a four-episode OVA between 2009 and 2010.

Ingrid is member of an organization who opposes the Taimanins. She has been tracking down a traitor of her organization, Sabato Kiryuu, but in his fight against him, she ends up falling for both a decoy of Kiryuu and a trap in the form of a disguised Kiryuu pretending to be a civilian human girl. Caught in his clutches, she is subject to exquisite, brutal torture and rape. Kiryuu has also as hostage Murasaki, a beautiful Taimanin which he also tortures and rapes in similar fashion.

Produced by Pixy. Animated by Anime Antenna Iinkai. Directed by Tsukasa Kaidou.

Tropes used in Makai Kishi Ingrid include:

Absolute Cleavage: In her civilian outfit, Ingrid has a generous one which falls just one breath away of exposing her nipples.
Adaptation Distillation: The OVA is technically an adaptation of Taimanin Murasaki, however many plot points were removed due to time constraints. For example, Sakura was completely taken out of the OVA, and many of the scenes with Murasaki were removed. That being said...
Adaptation Expansion: The OVA gives a lot more focus on "Ingrid's route" from the game, including new scenes for Ingrid that was not present in the visual novel.
Alternative Continuity: Seeing as Kiryuu is still alive, and the fact that Ingrid has remained a virgin until TA3, it's safe to assume that this OVA is non-canon to the visual novel series.
Aristocrats Are Evil: Kiryuu loves to throw fancy parties for his aristocratic associates. The main events usually end up being a depraved rape show, which many of these aristocrats take pleasure in watching.
Ascended Extra: Ingrid goes from being the third-billing character in Taimain Murasaki, to being the main protagonist of this series.
Baby Factory: During the final episode, Kiryuu planned to subject Ingrid and Murasaki to this fate. The two would have been forced to mate with Kiryuu's creation, the cerberus-like hell hound, Nabelius, and give birth to an army of these creatures. But thank Edwin Black and Kurou Yatsu's timely rescue, they were spared from this.
Balloon Belly: Ingrid was subjected to this, twice.
Big Bad: Kiryuu Sabato, a traitor to Ingrid's faction which orchestrates her capture and rape.
Big Damn Heroes: Edwin Black and Kurou Yatsu in the final episode.
Blood Splattered Warrior: Murasaki in the second episode during her fight with Kiryuu. Unfortunately for her, Kiryuu laced his blood with a powerful aphrodisiac.
Death by Adaptation: Kiryuu was killed by Ingrid at the end of the OVA series, but he is still alive in the visual novel series.
Death Seeker: By Episode 3, Ingrid is begging Kiryuu to kill her rather than keep torturing her.
Demoted to Extra: Although this is a loose adaptation of Taimanin Murasaki, the titular character of the game is made the Deuteragonist in this anime. Sakura was completely removed from the OVA, despite being a main character in TM. Also, Asagi was only briefly mentioned in this, but unlikely the visual novel, she does not make an actual appearance. This is mostly done to give Ingrid more screen time.
Deuteragonist: Murasaki Yatsu, which is also being tortured by Kiryuu and his allies, is given substantial focus.
Enemy Mine: If only briefly, Kurou and Edwin Black team up against Kiryuu in Episode 4.
Establishing Character Moment: The first scene shows that, though unconcerned with demons raping women, Ingrid still has some soft spots of kindness towards children.
Fanservice Extra: The woman being raped by a demon at the start. The demon doing the deed decides to vanish when Ingrid seems annoyed at him for raping her in public.
Fat Bastard: Ingrid is forced to prostitute herself for one of Kiryuu's associates in Episode 4 which have a massive belly. The man does not speak, and you don't even see his face, but anybody who hired a prostitute from Kiryuu is heavily implied to be evil.
Flash Step: Ingrid pulls this off in the first episode.
Four Eyes, Zero Soul: Kiryuu wears glasses and is a treacherous rapist and torturer.
Half-Human Hybrid: Kiryuu turned into a half-demon of his own will to make himself more powerful.
Hell Hound: Nabelius, a cerberus-like demon created from Edwin Black's DNA. Kiryuu created this creature for the purpose of destroying Edwin Black.
Hero Antagonist: Averted with Murasaki, which is basically just a fellow victim like Ingrid.
Jack Bauer Interrogation Technique: Kurou interrogates a pig man this way to discover Murasaki's localization in Episode 3.
One-Woman Army: Ingrid was able to fight off legions of Kiryuu's demons in the first episode.
Naughty Tentacles: Several of the monsters and even Kiryuu himself have tentacles which they use for sexual purposes.
Sex Slave: Kiryuu forced Ingrid and Murasaki to be this for most of the anime.
Spin-Off: To the main series. It's even more of a spin-off than the game is based on since it focuses on a route based around a minor character.
Stripperific: Ingrid's combat outfit exposes her panties and even a good portion of her nipples.
Swallowed Whole: Kurou is apparently killed by Nabelius in this fashion. The ending implies he allowed that to happen so he could kill it from the inside.
Undying Loyalty: Kiryuu believes Ingrid has this for Black once she refuses to help him against Black and demands to be killed instead.
Villain Protagonist: Ingrid. While Ingrid is Noble Demon, she still works for Edwin Black, which technically still makes her a "villain" from the Taimanin's point of view.
Wouldn't Hurt a Child: Ingrid couldn't bring herself to hurt a little girl in the first episode, unfortunately her, said little girl was Kiryuu in disguise.