Sigma (シグマ,, Shiguma?) is a member of the Decay of the Angel and the general manager of the Sky Casino. Sigma is a young person with long straight hair that reaches their waist. They appears to be kind to their customers at the Sky Casino, given the fact that they gave a customer another chance by saying that the game is invalid. They also appears to have a strong sense of ownership. Because they have no memories, no family, and no friends, Sigma's greatest wish is a reason to live.