If. They insist. Perhaps he's being rude, intruding upon them. His head tilts back in silent laughter and delight that he cannot control--which beats melting in front of yet another person--and he shrugs again. What a worrywart the human is. They resemble what Frisk might look like when older, come to think about it.

He waves a hand at the sky a second time, smile not fading, and turns to go. ...Away from the door he exited from. Gaster is more than willing to give the human space. Not to miss the rain. The respite could end at any moment, he must seize the day.