Nightmare had been watching you for the past several hours you'd been messing around with the others Cross, Error, Horror, Dust, E.T.C but he had a very soft spot for you he had a deep feeling a need to protect you, at times when you'd say certain things that he'd either blush and roll his eyes or simply say something back that was similar to what you said and smile you are killer sans someone nightmare has deep feelings for but doesn't admit it (this is a fanon A.U)