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Christa's backstory has been retconned in MORE BLOOD from Haunted Dark Bridal. In Haunted Dark Bridal, Christa only appears in Subaru's dreams and flashbacks of the time when he was with her. In MORE BLOOD, Christa willingly married Karlheinz.
Christa has been described by her son as being the most beautiful before Karlheinz raped her and gave birth to Subaru, she has a somewhat slender and mournful appearance. She also has white and pink hair and red eyes, matching her son's. She's usually seen with her hair tied up in a bun, held up by what looks like to be a frilly red hair band on the top left of her head. She has one long piece of hair, reaching down to her knees, let loose in the front that splits into two and intertwines with itself.
Christa wears a black and white velvet dress that extends outwards instead of clinging to her body. Its straps are of diamond shape patterns and various in size depending where they are. She even has connected from her necklace, covered in small red roses, to her dress in the middle. She also wears a type of light, transparent, blue sheer fabric around her arms, with white gloves that come almost up to her shoulders.
Despite her innocent and meek appearance, Christa has shown signs of a strong pride. This is shown in an infamous dispute she had with Cordelia about Karlheinz, where they argued about who he truly loved. This could be a bit surprising as she is usually portrayed as a meek, quiet person who is constantly in poor health.
True to this, Christa's mind has been torn apart due to the betrayal by her husband. At the revelation that she was used merely to produce a child out of incest, she would have fits and psychotic episodes, where she couldn't differentiate between identities and lost sense of the present. She is also revealed to have a more malicious personality, having deceived and poisoned Yui when she was under the delusion that Yui was Cordelia.
However, she had moments where she was gentle with her son, resulting in Subaru's view as a child that it was just him and his mother alone in the world. Although she loved her son, she gave him a silver knife and begged him to kill her.
(Spoiler information) Due to her beauty, Christa was lauded amongst the vampires as the 'White Rose'. In the retcon, she was happy to become Karlheinz's bride, but was then disgraced — she knew even before marriage that Karlheinz had researched her. Following Subaru's birth she started to lose her mind because of the realization that her husband never loved her. Realising her actions and the truth about her son's lineage, she would see her son as 'filthy' and often treated him as such.
In Subaru's DARK FATE route, during one of her psychotic episodes, she mistook Yui for Cordelia and begged Yui to stay away from 'that filthy person', referring to her son.
A possible explanation for this is in Haunted Dark Bridal, it is strongly implied that Karlheinz locked Christa up and broke her down mentally, causing her to go mad. She couldn't differentiate between people and saw her son as a filthy stranger, a result that is replicated on Yui in one of the bad endings.
In Subaru's DARK FATE route, she explains to Subaru the circumstances surrounding her marriage to Karlheinz as she lies dying. It is revealed that she knows she was being used, but loved her husband nonetheless. She also tells Subaru that she loves him before dying. There is a realization that Christa has been nothing but a victim of one of her husband's experiments. 
She is described as having a ghost-like presence.
To further complete his plans, Karlheinz turned to his cousin, who calls him "nii-sama". deceiving and seducing her into believing he truly loved her. When she realised the true nature of their marriage, the conflict between her emotions broke her down and caused her to go insane. Despite this, she still loves her husband. It could be said that Karlheinz cultivated in both Cordelia and her (and maybe Beatrix), a behaviour of obsession and devout loyalty, as these women loved him dearly only to be used and constantly lied to. Karl indeed did love her as revealed in Subaru's DF Vampire ending. As he lay dying he tells Subaru that he represents both Christa and Karl himself. These are words of a proud father who loved both his child and the mother dearly. Experiment or no experiment, Karl loved Christa until he died.
In times when she wasn't mad, Christa loved Subaru and doted on him. Her insanity caused her to have fissions in her personality: she could be gentle and meek one moment before becoming spiteful and malicious the next. For example, during perhaps one of her delusions, we can see her praising her son; that Subaru was a good boy and 'one day he whose blood is more disgusting than someone's else could be a respectful person'.
She has always begged her son to kill her and her husband - to the point of even giving him a silver knife that can kill vampires. Subaru himself has never been able to fulfill her request to end her suffering because he loves his mother and so he is tormented by guilt. In the MORE BLOOD manga, Christa often had fits when she was alone. She would worry about Subaru and desire his presence; but because she was unstable, whenever she saw him, she had even more fits. This was because Subaru looked like her beloved cousin, Karlheinz.
- "You are such a gentle boy." (To Subaru)
- "You are filthy, Subaru!" (To Subaru)
- "The only person he loves is me!" (To Cordelia)
- "And I was happy to become his wife." 
- She sometimes calls Karlheinz "Onii-sama."
|Sakamaki Brothers||Ayato Sakamaki • Kanato Sakamaki • Laito Sakamaki • Shu Sakamaki • Reiji Sakamaki • Subaru Sakamaki • Kino|
|Mukami Brothers||Ruki Mukami • Kou Mukami • Yuma Mukami • Azusa Mukami|
|Tsukinami Brothers||Carla Tsukinami • Shin Tsukinami|
|Others||Karlheinz • Beatrix • Cordelia • Christa • Richter • Seiji Komori|