They shrug. They don't know how to react otherwise, but they're sure even if they are, S4 will grow into being the best.

"Mm-hmm." Frisk scoots over, leaving him generous space to seat himself. Only after that will they actually try to touch him--that is, gently leaning over to press themselves against his side. Their soft warmth is probably a novel sensation, though they're not thinking of that.