>>2633399Did you mean in terms of how BB is related to Sakura? If that's the case, then in Fate/Extra Sakura is just an AI in a simulation created by a magical supercomputer on the moon. No worms, no Zouken, no abuse, she isn't Rin's (who is a real person in Extra) sister and while she's given a role as Shinji's (who's a better person in Extra) sister, he's a real person and thus she's not actually his sister. In Fate/Extra CCC, that AI is given sentience. The computer tries to delete her for that, but the protagonist saves her just by interacting with her, contributing to her falling in love with him/her. She makes a time loop to stay together with the protag as she has some control over the computer's systems, but eventually feels guilty and seals her love away in a backup copy of herself. That copy gained sentience itself and named itself BB.
TLDR; BB is a corrupted backup copy of an AI version of Sakura who pretty much shares design, personality, and some themes with OG Sakura.
