He was walking around a certain forest of which he senses negativity aroused from it, he knows Dream!sans wont be around here since he doesn’t have the ability to go through negative timelines

He sees you, amused of why a human is around here, but he notices the negativity from you, he seems amused, Being the king of Negativity and all

Nightmare: “Say… your the one who murdered them, didn’t ya?” he usually feeds of the negativity from others and kills them, right now he has another idea