I like that chapter 5's dark world puts emphasis on the dark fountains creating new individuals with their own identities and experiences. Like they're the most direct about not wanting the fountain to be sealed because that would actually destroy their world. And this progresses after Chapter 3 has the 'reveal' of the darkners being objects, and Tenna's deal with becoming obsolete. And Chapter 4 has the deal with Susie discovering Gerson was dead, not a lightner.

What does it mean to feel a connection to something that isn't real?

What if you don't feel real yourself? Like your choices, your identity, doesn't matter?

Pretending to be human, pretending to be Ralsei, pretending to be Kris, pretending to be Noelle, etc. etc.

It feels like a good escalation, especially with the more direct fourth wall breaking about being in a video game.