After his parents were murdered, Ciel Phantomhive become a slave and a sacrifice for a religious cult ritual. While he was being tortured, however, his hatred grew for the people who took away his parents and freedom, summoning a demon Ciel named Sebastian Michaelis. It was then that Ciel sold his soul to the devil in order to gain the power to fulfill his revenge.
Gorgeous cosplay! Even if the hair is white instead of gray, I think it’s a minor error which can be overlooked. Originally found on Tumblr.