At first I was thinking just like Manchura above, this is the Matrix, but those who left have their avatars turn into zombies.
Perhaps it’s a bit nutty, but then it’s actually an interesting take because unlike other zombie series, it explains why they don’t rot (and other unphysical fiction-like aspects).
While most series tend to approach the unphysical aspects with the explanation of it is how it is, stop thinking, look at how they’re smashed/shot/give chase; this one actually has something that tie things together quite neatly. Assuming her father’s explanation is true that is.