Untitled

like just compare the two yourself:

chapter 4 ends with kris and susie on the same screen. split, yes, but the same screen regardless. when susie's screen disappears, kris attempts to leave, to chase after the one person that's made the darkness bearable. this may be the closest they are to abandoning the plan and breaking the promise

all because of susie

(this is brainrot territory, but note that kris tries to leave via the window, something that allows light into their dark room)

and then in the din of the pouring rain, the caller tells kris outright:

'don't forget'

kris has to be verbally reminded to stay on track.

because otherwise, they want to leave to go to susie.

in contrast, chapter 5 ends with kris and susie on completely separate screens, with susie shutting the door (which allows no light in, unlike a window) between them. susie does not share presence with kris in the ending. it is them entirely separate.

the credits then play field of hopes and dreams, notably all piano (kris's instrumental stand-in)

the piano plays its richest harmony of 'don't forget' for susie's arrival in castletown as if celebrating her, giving light to her presence and friends

and then as it plays 'don't forget, i'm with you in the dark' for susie, it transitions to kris in the darkness

this time, there are no words. there's no 'don't forget' being audibly said whether in the credit song or in the game itself (every chapter has had 'don't forget' present in the ending in some way or form)

this time, 'don't forget' comes in the form of the lonely piano melody that ends in the same fashion as chapter 4's sanctuary melodies and the very song that kris played on the piano:

'don't forget, i'm with you in the...'

and it being a piano melody almost seems like a self-reminder to kris. kris doesn't need to be reminded by someone else anymore. with this development, kris is committed to the plan, the promise. the piano notes are all they need to remind themself:

they're alone

they have a promise to fulfill

they won't hesitate anymore