Here's some fact-free speculation while I'm waiting for the kettle to boil.
Parts of Cynthia's entourage is definitely wrapped up with Callista (Otto certainly, the masked servants (
Alexander's sisters?) probably), and it seems entirely plausible that Delilah planted the bracelet for Kane and Nadia
could be the hacker, maybe at Cynthia's behest, maybe not.
And then there's Lola. Silent, ignored Lola, who is pointedly introduced by name and with a close-up and then never mentioned or seen again (so far). Maybe just because the dev has forgotten about her, maybe not.
Kiyomi recognized at least
one of them by their movements although they'd hidden their appearance, but she's confident that only one other person would do so and that that person is "not a concern".
Could be one of the masks, could be Lola, could even be Otto himself in his conveniently concealing clothes.