The Ciel Phantomhive that fans have been watching throughout Black Butler, also known as “O!Ciel” or “Our Ciel” by the fandom, is the twin that formed the contract with Sebastian.

The story of Ciel Phantomhive’s death dates back to December 14, 1875, when he was born. It is little known that he was not born alone. He was born after his twin brother, Ciel. The elder Ciel ...

The contract between Ciel and Sebastian is the basis of Black Butler's premise. Here's a closer look at the details of this demonic contract.