D is believed to be TENka's Anti-Hacking System, and Kleya is comletely comfortable with letting them continue to believe this. Kleya Smith has mentioned that it is actually her system giving the impression that she built it. D looks like a dragon and is an AI. It activated when SuperBug was hacking Danni Morretti during the Game Trials. It caused the server to shut down but was able to log enough information for TENka to determine where SuperBug was located and if he was a part of the Deconstruct Me group.
In LiFe, D tempts Kleya, giving her options to hack and acts as a foil to her. One instance of this is when he gave "insert" as an option to fix Mae's broken avatar. In addition, D runs the ship that Kleya is on, while she's logged into LiFe. It also keeps track of strange weather patterns, the magnetic pole shifts, volcanoes, etc.
In Reality, D can speak directly to Kleya's mind using her cyborg-type equipment. She responds aloud, however.