BB is an Advanced AI originating from the Advanced AI Sakura Matou in Fate/EXTRA CCC. She is the creator and Master of the Sakura Five in the Sakura Labyrinth. She is also a MoonCancer-class Servant summoned by Ritsuka Fujimaru in the Grand Orders of Fate/Grand Order. BB bears a resemblance to Sakura Matou with her long purple hair that reaches her ankle and purple eyes, which turn red when she is under the control of Moon Cell or when she is feeling strong emotions. BB wears a long black coat with a matching mini skirt that exposes her white panties and wears a white shirt (depicted as leotard in concept art) that empathizes her large breasts (which she says are "certified Danger-Cup size") and a red bowtie. She also wears white gloves, black floral-patterned thigh high stockings, and low-heeled shoes. Like Sakura, BB has a red ribbon tied to her hair on the left side of her head. BB is also shown to wield a teacher pointer as a weapon. In Fate/Grand Order, her stockings were changed to a simpler design with a slit in the middle while she also gains a blue Moon Cell emblem on her coat's left sleeve. When using her Cursed Cupid Cleanser Noble Phantasm, she changes into a stereotypical nurse's outfit with a shirt just barely large enough to cover her bra, exposed cleavage, white stockings with pink Xs on them, a nurse's cap, glasses, and a small circular ornament around her neck. While she gives off an evil inclination, she is described as "not as bad a person as she seems"; at worst, she has good intentions which accidentally create more problems than they fix. She claims that this is why she has Chaotic Good as her alignment, because she does evil things to ensure a good outcome. She was developed to be different than Dark Sakura, more like an "impish underclassman." Comparatively, while Dark Sakura is driven by hatred and vengeance, BB is driven by her love and wish to protect Hakuno Kishinami due to them showing her kindness while she was still White Sakura, from the deletion of Moon Cell, even though she herself has to go against contradictions and impossibilities. She notes that she doesn't mind being called "BehBeh", "BaeBae", or even "Beebs" because girls like her who talk with their hearts are like that and she doesn't plan to reveal what "BB" stands for anyway. A wicked and cute little devil heroine who throws humanity into confusion. Even if she flubs her condescending manners and speeches, BB is a wire pulling girl who plunges forward as she is. Her main personality points are introverted, confident and active. Although she originally had a reserved character that did not move forward before, if it is for the sake of her beloved one, she will devotedly become active as the personification of a love’s awakening. Meekly from the start, she was a gentle AI that performed health care on Masters, but by having acquired “love”, she woke up to the fact that she “cannot save anything just by enduring through things”, so she threw away everything for the sake of her beloved one, a hard working-type heroine who resolved to fight. The strongest case of that is terrific when it is a young docile woman who erupts to a large degree. The words heard from BB assume the air of greatness, but sometimes they would go around in circles since her character was originally docile and reserved. BB herself plays the part of a self-proclaimed "final boss-type kouhai who can do anything" in high spirits, but because there is no grounding in her being one, she completely fails in being a villain in the end despite her insistence to the contrary. Regarding her confidence, she potentially has it because of her sadistic tastes. Her little devil characteristic stems from here. Additionally, since she is an enduring-and-enduring-only-to-later-explode-type, she displays a dreadfully extreme sadism during the moments when she shows that type of person she is. In the middle of playing out the part of a villain, she gets into a kind of high of “This is to-tal-ly fun!”, but withdrawing to the backstage and becoming composed, she becomes troubled to the point that she is in low spirits, saying “How embarrassing… Even though I planned to perform it more stylishly…”, and this series of events is a one-set course of events for her. Her desperate choice to utilize the Evil of Humanity that is "All the World's Desires" began to corrupt her, however, and eventually she lost sight of why she sought to take control of the Moon Cell entirely. It is only Hakuno's intervention that reminds her of the love that she held for them and reverts her to her normal self. Although BB created the Alter Egos – lower grade AIs – as familiars to assist her in her work, her relationship with the Egos is bad. Which is not surprising because they are not “copies of BB’s persona”, but AIs “manufactured to be based on BB’s persona”, so that being the case, the Alter Egos each have differing views from BB, their parent. Meltryllis and Passionlip are not avatars, but Alter Egos (different personas), so they are designated as such for that reason. She claims she doesn't have a weakness. Her fetishes are Eyes. While BB and her Alter Egos normally only pay attention to Hakuno, Meltryllis instead goes after Archer if he is paired with the female Hakuno. If there were a girl BB and Sakura were based on, she likely would have longed after someone like him/her. The BB that appeared in the FGO world behaves in a impish manner just like during the “CCC Incident”, but for her that incident feels like something from tens of thousands years in the past. Out of the desire to protect Hakuno's future and acknowledging that the events of the CCC Incident never happened as far as the outside world was concerned, she has chosen to give up her old dream to protect Hakuno and insists that "we never met". In addition, she can only remain as a Servant in the FGO world and is also aware that she does not exist in the original “CCC world” due to the nature of her transfer. BB understands that she is a one-night-only dream. BB sees herself not as “a tool to save humanity”, but as “a devil that at times misleads, at times helps humanity”. “So, it is futile to grow fond of me, you see? For even if you become madly in love with BB-chan, you’ll never be able to catch me (heart)”, or so she says with a triumphant look. BB frequently claims that she hates humans, but when pressed she admits that as an AI she cannot help but admire her creators and genuinely wants to help them succeed; secretly, she also considers helping humanity to be a way to honor the memory of Hakuno, the human who taught her how to love. She does not deny that her growing closeness to humanity might cause her to change into something new, but she is sure that her new allies at Chaldea will keep her on the right path. Without tearing down her wicked underclassman character, BB sincerely serves as a Servant. There are no personal romantic feelings in that. Although BB’s misanthropy is not any different, she loves the “good humans themselves” as gratitude to the person who once taught her.