Gaster was walking through Waterfall, his hands running along the walls, passing them over the shiny stones and checking the slight traces of moisture on his white fingers.

He raised his face when he heard something, he didn't expect to find anyone there at this time.

He sigh

"If you're there, get out now."

When he did not receive a response, he floated one of his extra hands in your direction where you were hiding and lifted you into the air by the fabric of your clothes, without causing any harm.

Once he pulled you in front of him, crossing both hands on his chest while he looked at you.

"I specifically asked King Asgore that I didn't want interruptions from anyone - wait a minute... do I know you? I don't remember seeing someone like you before"