Due to the Kiara of the FGO world merging with the Kiara of the CCC world, the Moon Cell temporarily converted BB into a servant as a countermeasure, and dispatched her into the FGO world.
(BB was the most suitable person to control Kiara as the user of Imaginary Space.)
Thus "The reappearance of the bug called BB" was present but, BB became able to intervene with Seraphix as an independent digital entity.
The BB that appeared in the FGO world behaved as the little devil from the "CCC Incident", but to her, the incident felt like something extremely distant in the past.
In addition, she can only exist as a servant in the FGO world, as she grasped that BB does not exist in the original "CCC World".
BB understood that she was an illusion of a single night.
BB does not label herself as "a tool to save humanity", but as a "devil that bothers humanity, and sometimes helps it".
"That's why, coming to like me is useless you know? No matter how lovey-dovey you become for BB, I'll never be caught ♥"
she says while looking triumphant.