Blue hoodie, white bone, and Frisk is running. It's an impressive pace, for their tiny, stubby legs, dragging them over land to launch face first into Sans' back, unaware of what the skeleton might think at the weight of a child suddenly pressed into his back, unaware that Chara is here, is a person again, is anything but a voice in the back of their head urging them to violence.
"Sans! Sans, you're here, you're here!" It's muffled by ketchup scented fabric, but it doesn't matter - Sans is here, which makes things OK, at least a little. Tiny arms wrap around his ribs as tight as they can, and it's clear Frisk isn't letting go of their own free will. “Sans, I missed you!”
It’s only been a short while in their perception of time since they were in the Underground but Frisk has always been a sensitive child.