Lets see who would cheat~
○gender natural readerSebastian~
Hell yeah he would depends on your view of him but in my opinion he is a man hoe in the anime...If you cheat on him~
Honestly idk if this guy has feelings but he would have this sad aching feeling in his heart when he sees you.Ciel~
Nah way too much pain to do that to you he wouldn't want hurt you he loves you and respects you.If you cheat on him~
He probably be disappointed that frown would get bigger than what it normally is. He would act like he doesn't care but he does he will get over it because of Sebastian and distract himself with cases from the queen.Grell~
Hell yeah when you start dating no matter how long and Sebastian shows a tiny bit of attention to her bye (n/n)..If you cheat on her~
Comes crying buckets to the Phantomhive manor to Sebastian arms. Sebastian will be angry at you though. Grell is a whore she might care you never know.