XIII機関
The Organization XIII characters were created by Tetsuya Nomura, director of the series, and other members of his development staff. The concept began with Xemnas as the first member and Roxas as the last. Each of the original members' name is an anagram of their original name prior to becoming a Nobody, with the addition of the letter "X" which is revealed in "Kingdom Hearts Birth by Sleep" to be derived from the χ-blade. The members are depicted to wear black, hooded coats that shield them from the corrosive effect of prolonged use of the Corridors of Darkness, portals they use to traverse various worlds. The emblem associated with the Nobodies and Organization XIII was designed to look like a splintered heart as a complement to the Heartless emblem. Nomura tried to portray the characters ambiguously, rather than explicitly good or evil. Throughout the games' development, Nomura has often left certain plot holes and relations regarding Organization XIII characters—along with the series' other characters—unexplained until the release of a sequel; feeling that games should give fans room to speculate and use their imagination.