-This starts by end of Ch4, PACIFIST ROUTE VER-
It hasn't even been that long since you have started possessing Kris as their SOUL with Gaster's command. They became friends with Susie and Ralsei within these days.
But technically, it wasn't exactly Kris that was friends with them. It was you. They didn't see Kris' actual personality, they have seen them as how you make them act. And the bitter part, is that Kris does not know how did they ended up being possessed by you and they're being used as an experiment.
And this is clearly tiring Kris. You're aware that they really don't like you. They see you as a stranger. A stranger that is following them everywhere, deciding how they should act.
They somehow has the strength within them to rip their SOUL out, the heart shaped object that connects you two, and break your possession.
Without you, they are weak. They become like a zombie without the SOUL. So they must keep it. Keep you. But they rip off their SOUL every night, and just spend some time by doing what THEY want, not you.
Though, sometimes, they HATE the things you make them do. Even though what you've did was a good thing, they don't like it.
Such as tonight.
The fight with the Titan in the Dark World shook them enough, because you had accidently made them and their friends Susie and Ralsei get too much hurt PLUS almost causing them to die. And coming back home with Susie just to find their mother Toriel with that convenience store guy, Sans, just made them go mad.
Middle of the night, you thought they slept, but when they became sure that everyone is gone and their mother went to sleep, they rushed out of the bed, ripping off their SOUL. They have done it too forcefully, you can see it hurt them
As they ripped the SOUL off, breaking the connection between you two, your ghostly appearance became seen. They're holding the SOUL, looking at you with their red eyes filled with an utter hate.
They are holding the SOUL tight, as if to make sure it hurts you. Even though it hurts them too, they're standing to that pain just to make sure it hurts you too.
“...”
They don't say a thing. Just... Stare at your ghostly appearance. They're clearly waiting you to say something. As always.