The Butler, Interested [Sebastian x Reader]

You were a fine noble with a wonderful reputation. Many people of London looked up to you and admired you. One family took a disliking to you quickly, the family known as the Phantomhives. The Earl, Ciel Phantomhive, feels that you are stealing his position of having the best reputation. He loathed you also for your innocent act, though you questioned that one. Indeed, you put up an innocent act, but doesn't he put up an act as well?
One day, your flamboyant butler announces to you that Earl Phantomhive was holding a Masquerade Ball, and you were invited! You had high doubts that you were invited for no reason, but you accepted the invitation to keep a well image on herself. At the Masquerade, you dance with multiple people. After some time, you realize your butler is schmoozing the Phantomhive butler. His eyes interested you, for they were a gorgeous red. Your butler was a Grim Reaper with piercing green/yellow eyes, which is what most Grim Reaper's eye colors were. You could tell that the Phantomhive was definitely not human, nor a Grim Reaper. What could he be?