When S-4 finishes and turns to see Sans is completely passed out, he doesn't even complain or try to poke him awake. After everything that has happened today, they both deserve the rest. And Sans trusting S-4 enough to let him read the bedtime story... it feels like a pretty big deal. S-4 can't help but feel a surge of pride as he puts the book down and slings an arm around his brother's shoulders.

Having him close like this, happy and healthy and safe, makes S-4's usual energy start to wane into sleepy affection. It isn't long until he's dozing next to his brother, enjoying the moment of peace as best he can.