Chara misses it, just as they miss the other's discomfort from their presence. In a better state of mind they might think to parse that through what they know of the apparently common-to-Frisk's tendency to sacrifice their comfort for others, but at this time they take the agreement at face value.

There's very little movement from them, beyond the up and down of their breathing, and their eyes slowly, slowly closing, fluttering open in hypnic jerks before falling again. They lose track of time.

And then they fall asleep, utterly exhausted. It's either a testament to how tired they are or how much they've come to trust this Frisk or how much they don't care what happens to them at the moment or all three, that they've allowed themself to become this vulnerable.

Their breathing is utterly shallow, and their face for once relaxed - it's currently dreamless. It looks like a mask.