In the context of vtubers, 'kayfabe' is used to refer to the artificial elements of the persona. Like pretending to have a crush on someone you're just friends with because it makes for good content
...Okayu and Korone spent, like, their first 20 months at Hololive acting like they had the same kind of joke-flirting relationship as, say, Aqua and Shion, but as they've opened up about their relationship it's looking more and more like they've been dating this whole time