Just as Anastasia had been speculating for a long while now, there were other people around in this palatial home of theirs.
She was sensing other presences aside from Zen's from time to time, but since she felt like he wouldn't disclose this any time soon, she just chose to zip her mouth and investigate on her own. Contrary to her initial belief, though, these presences weren't actually that of humans.
They turned out to be these robots with artificial intelligence, designed to resemble humans as close as possible. What's more, they all seemed to be carefully and meticulously trained or programmed to effectively fill in the shoes of houseworkers.
Anastasia could say so since that's exactly what she's seeing at this very moment.